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31735 Publications
Dosimetric comparison of two planning target volume margin recipes for prostate radiotherapy
Ahmad, A.; Troost, E. G. C.; Löck, S.; Agolli, L.; Valentini, C.; Enghardt, W.; Geyer, P.;
Background and Purpose: Planning target volume (PTV) margins are applied around the clinical target volume (CTV) to cover organ motion and patient set-up related random and systematic uncertainties that occur during the course of fractionated radiation treatment. In this study two PTV margin recipes were compared retrospectively on the basis of a prospectively acquired data to investigate the effectiveness of positioning protocol for the prostate cancer patients.
Material/Methods: In total 12 patients with prostate cancer were registered for a prospective imaging and positioning study that was approved by the local ethics committee (EK272072014). All patients received 74 Gy(RBE) in 37 treatment fractions. Overall, 379 daily in-room cCTs with the patient aligned in treatment position were available for analysis. All cCTs of a patient were registered with the planning CT (pCT) in 6 degrees of freedom using bony landmarks. The prostate, bladder and rectum were contoured on all CTs and transferred from the cCTs to the pCT. The union of overlaid prostate contours of all cCTs resulted in the composite prostate contour. First, PTV margins were determined such that 95% of composite prostate was covered for 90% of the patient population by an anisotropic expansion of the pCT prostate contour (Fig. 1). Interfractional prostate motion and related systematic and random uncertainties were assessed. Second, PTV margins were calculated using van Herk’s [1] formula. Finally, volumetric modulated arc therapy plans were generated and recalculated on the cCTs using both PTV margins recipes, and coverage (D98%) and hotspots (D2%) in the CTV as well as dose volume constraints for bladder (V65Gy, V70Gy and V75Gy) and rectum (V50Gy, V70Gy) were compared (Fig. 2).
Results: PTV margins along left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions were 4.3, 5.3 and 4.8 mm using the first approach, and 1.4, 4.8 and 3.5 mm for the second approach, respectively. Target coverage was fulfilled for all but one cCT using the first approach, but it was not fulfilled for 6/379 cCTs for the second approach. Dose-volume constraints for bladder and rectum were fulfilled for the second margin approach but for the first margin approach V70Gy for the rectum was not met sometimes (Fig. 2).
Conclusions: Using the composite prostate coverage approach, robust PTV margins were derived since they also took rotation and deformation into account and thereby ensuring CTV coverage over the course of treatment.
Keywords: Planning target volume, Endorectal balloon, Interfractional prostate motion, Control CT, Radiotherapy

Publ.-Id: 26219 - Permalink


Thermal convection in liquid metal batteries
Personnettaz, P.; Weber, N.; Koellner, T.; Nimtz, M.; Weier, T.;
Liquid Metal Batteries ( LMBs ) are a promising electrochemical energy storage technology, built as a stable density stratification of two liquid metals separated by a molten salt. In this work, we focus our attention on thermal convection that appear inside Li||Bi LMBs. The chemistry of the cell is first presented. Then all possible thermal phenomena are discussed, with a continuum mechanics approach. The temperature profile is first defined in the hypothesis of pure conduction. Moreover, in order to take into account thermal convection inside the cell, the multiphase solver multiphaseInterFOAM is extended. The results of this solver are compared to the one of a pseudo-spectral code. Finally the first result of thermal convection in Li||Bi LMB is presented. The future work on transport phenomena in LMBs is also briefly summarized.
Keywords: thermal convection, transport phenomena, liquid metal battery, numerical model, OpenFOAM.
  • Lecture (Conference)
    openFuelCell workshop, 24.10.2017, Jülich, Deutschland

Publ.-Id: 26218 - Permalink


NTCP modelling and external validation of early side effects for proton therapy of brain tumours
Dutz, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Lühr, A.; Vermeren, X.; Geismar, D.; Timmermann, B.; Löck, S.;
Purpose: To identify patients who are likely to benefit most from proton beam therapy (PBT), based on the potential reduction in normal tissue complication probability (NTCP) compared to photon therapy. The NTCP models required for this decision were developed using clinical data on early side effects for patients with brain tumours who underwent PBT.

Material and methods: Two cohorts of adult patients with brain tumours who received PBT were included in this study: 113 patients treated at University Proton Therapy Dresden were used for model training and 71 cases from West German Proton Therapy Centre Essen were used for external validation. Moreover, volumetric modulated arc therapy (VMAT) plans were retrospectively created for all patients to predict the potential reduction in NTCP when applying PBT. The radiation-induced early side effects alopecia, erythema, pain and fatigue were investigated. The occurrence of these side effects was correlated with different DVH parameters of associated organs at risk (OAR), such as skin and remaining brain. NTCP models were created using logistic regression and the area under the receiver operating characteristic curve (AUC) was used to assess their prognostic ability.

Results: The NTCP models revealed significant correlations between the incidence of alopecia grade 2 (figure a) as well as erythema grade≥1 and the DVH parameters D1%, D2%, V15Gy and V20Gy of the skin. The V20Gy models showed a very good discrimination on external validation for both endpoints (AUC≥0.75, figure b). No correlations between DVH parameters of the remaining brain and the incidence of fatigue or pain were found. Dose comparison between PBT and VMAT showed large differences in both training and validation cohort, especially in the remaining brain. The mean brain dose of the PBT plans was significantly lower compared to VMAT (median training: 6.9Gy vs 18.6Gy, median validation: 8.5Gy vs 16.0Gy; p<0.001). For alopecia grade 2, plan comparison between PBT and VMAT predicted a potential median NTCP reduction for PBT of approx. 5% (range: -39% – 32%) in the training and 1% (range: -25% – 37%) in the validation cohort. A reduction of NTCP for alopecia grade 2 for PBT by more than 10% was observed for 12/113 patients in training and for 9/71 patients in validation.

Conclusion: Plan comparison showed a large reduction in dose to the brain using PBT instead of VMAT. We found significant correlations between the occurrence of early side effects and DVH parameters of associated OARs for patients with brain tumours receiving PBT. A relevant reduction of NTCP (>10%) for PBT was calculated for approx. 10 % of the patients. However, due to the large range of NTCP reduction, patient individual calculations are mandatory. After inclusion of more relevant late side effects and neurocognitive changes, these models may be used to identify patients who are likely to benefit most from PBT [1].

[1] Langendijk JA et al. (2013) Radiother Oncol 107, 267-273.
Keywords: NTCP modelling, early side effects, proton therapy
  • Lecture (Conference)
    ESTRO37, 20.-24.04.2018, Barcelona, Spanien
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S266-S267
    DOI: 10.1016/S0167-8140(18)30821-1

Publ.-Id: 26217 - Permalink


Evaluation of fluorine-18-labelled alpha1(I)-N-telopeptide analogues as substrate-based radiotracers for PET imaging of melanoma-associated lysyl oxidase
Kuchar, M.; Neuber, C.; Belter, B.; Bergmann, R.; Lenk, J.; Wodtke, R.; Kniess, T.; Steinbach, J.; Pietzsch, J.; Löser, R.;
Accumulating evidence suggests an unequivocal role of lysyl oxidases as key players of tumour progression and metastasis, which renders this enzyme family highly attractive for targeted non-invasive functional imaging of tumours. Considering their function in matrix remodelling, malignant melanoma appears as particularly interesting neoplasia in this respect. For the development of radiotracers that enable PET imaging of the melanoma-associated lysyl oxidase activity, substrates derived from the type I collagen alpha1 N-telopeptide were labelled with fluorine-18 using succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) as prosthetic reagent. With regards to potential crosslinking to tumour-associated collagen in vivo, their interaction with triple-helical type I collagen was studied by SPR. A mouse model of human melanoma was established on the basis of the A375 cell line, for which the expression of the oncologically relevant lysyl oxidase isoforms LOX and LOXL2 was demonstrated in Western blot and immunohistochemical experiments. The radiopharmacological profiles of the peptidic radiotracers were evaluated in normal rats and A375 melanoma-bearing mice by ex vivo metabolite analysis, whole-body biodistribution studies and dynamic PET imaging. Out of three 18F-labelled telopeptide analogues, the one with the most favourable substrate properties has shown favourable tumour uptake and tumour-to-muscle ratio. Lysyl oxidase-mediated tumour uptake was proven by pharmacological inhibition using β-aminopropionitrile and by employing negative-control analogues of impeded or abolished targeting capability. The latter were obtained by substituting the lysine residue by ornithine and norleucine, respectively. Comparing the tumour uptake of the lysine-containing peptide with that of the non-functional analogues indicate the feasibility of lysyl oxidase imaging in melanoma using substrate-based radiotracers.

Publ.-Id: 26215 - Permalink


Multiscaled experimental investigations of corrosion and precipitation processes after loss-of-coolant accidents in pressurized water reactors
Renger, S.; Alt, S.; Gocht, U.; Kästner, W.; Seeliger, A.; Kryk, H.; Harm, U.;
In a joint research project of the Zittau/Goerlitz University of Applied Sciences (HSZG), the Technische Universitaet Dresden (TUD) and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the main emphasis is the time-related assignment of simultaneous and interacting mechanisms at zinc sources and zinc sinks at boundary conditions of a loss-of-coolant accident (LOCA) in German pressurized water reactors (PWR). The according experiments are carried out at semi-technical as well as at laboratory scale.
Zinc is used as a protective coating, e.g. for gratings in the containment, showing high corrosion resistance due to a gradual formation of passivating layers. In contrast, its long-term behaviour during LOCA changes significantly under the influence of the coolant chemistry of German PWR. As a consequence, according installations in the containment act as zinc sources due to corrosion. Released zinc ions change the chemical properties of the coolant and could e.g. lead to layer-forming depositions of zinc borates in the core, which increase the possibility of a hindered heat dissipation. For experimental and methodical investigations of these phenomena, the test rig “Zittau Flow Tray” (ZFT), a scaled sump model of a German PWR, was equipped with a full-length 3×3 fuel assembly (FA) dummy acting as core model, a preheater and a cooler component. Nine 4.4 m long fuel rod dummies simulate the decay heat by internal heating cartridges. This rig design enables experimental investigation of physico-chemical mechanisms considering coolant containing boric acid and zinc and their influence on the thermo-hydraulic processes in the reactor core at post-LOCA boundary conditions.
The time depending zinc release at hot-dip galvanized gratings (HGG) was investigated regarding their position (e.g. inside or near the leaking jet, freely suspended or submerged in the coolant) and their surface area as well as temperature and flow rate of the coolant. The experimental database allows the approximation of corrosion rates in dependence of HGG position and the accident-specific coolant leakage rate as well as the development of first mathematical approaches for the modelling of zinc sources.
Keywords: pressurized water reactor, PWR, corrosion, LOCA, loss-of-coolant accident, experiment, zinc, zinc borate, debris, deposition, precipitation, particle formation, chemical effects
  • Lecture (Conference)
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17)
  • Nuclear Technology 205(2019)1-2, 248-261
    DOI: 10.1080/00295450.2018.1499324

Downloads:

Publ.-Id: 26214 - Permalink


Speziation trivalenter Actinide/Lanthanide im Verdauungssystem
Barkleit, A.ORC; Wilke, C.
Im Falle einer Inkorporation radioaktiver Stoffe entstehen ernsthafte gesundheitliche Risiken durch deren Chemo- und Radiotoxizität. Um die möglichen toxischen Effekte besser abschätzen und letztendlich verhindern zu können, ist es notwendig, die Speziation dieser Elemente im menschlichen Organismus auf molekularer Ebene zu verstehen. Die Speziation beeinflusst die Aufnahme, den Transport, den Metabolismus, die Einlagerung und die Ausscheidung der Elemente.
Die Gefahr einer oralen Aufnahme von Radionukliden besteht durch kontaminierte Lebensmittel oder Trinkwasser. Deshalb haben wir die Speziation von ausgewählten dreiwertigen Actiniden und Lanthaniden (Cm(III) und Eu(III)) in den Biofluiden des Verdauungstraktes näher untersucht [1]. Die Biofluide wurden nach einer international anerkannten Methode (Unified Bioaccessibility Method, UBM) der Bioaccessibility Research Group of Europe (BARGE) synthetisch hergestellt [2]. Parallel dazu wurden natürliche menschliche Speichelproben zum Vergleich in die Untersuchungen einbezogen [3].
Die Speziatonsuntersuchungen von Cm(III) und Eu(III) in den Verdauungsfluiden wurden mit Hilfe der zeitaufgelösten laserinduzierten Fluoreszenzspektroskopie (Time-Resolved Laser-induced Fluorescence Spectroscopy, TRLFS) durchgeführt. Für Speichel wurde ermittelt, dass sich zum größten Teil (60-90%) anorganische Komplexe bilden, darunter dominiert ein ternärer Komplex mit Phosphat und Carbonat als Liganden und Calcium als weiterem Kation zum Ladungsausgleich. Organische Komplexe, hauptsächlich mit dem Verdauungsenzym α-Amylase, wurden ebenfalls nachgewiesen. Wenn die Speichelmischung den Magen erreicht, findet aufgrund des niedrigen pH-Wertes im Magen (pH<2) eine Dissoziation der Komplexe statt, Cm(III) und Eu(III) liegen dann hauptsächlich in Form ihrer Aquo-Komplexe vor. Aber ein kleiner Teil der Metallionen (ca. 20%) bildet trotz des niedrigen pH-Wertes Komplexe mit dem Verdauungsenzym Pepsin. Im Dünndarm, wo die eigentliche Verdauung und die Absorption der (Nähr-, aber auch Gift-)Stoffe in den Blutkreislauf stattfindet, werden die Metallionen hauptsächlich (ca. 65%) von dem Protein Muzin komplexiert, welches Hauptbestandteil der schützenden Schleimhaut (Mucosa) ist, und ca. 35% liegen als anorganische Spezies mit Phosphat und Carbonat als Liganden vor.

[1] C. Wilke et al., J. Inorg. Biochem. 175, 2017, 248-258
[2] J. Wragg et al., British Geological Survey Open Report OR/07/027, Keyworth, Nottingham, 2009, 90 pp.
[3] A. Barkleit et al., Dalton Trans. 46, 2017, 1593-1605.
Keywords: digestive media, speciation, europium, curium
  • Invited lecture (Conferences)
    2. Workshop - Helmholtz Cross Program Activity, Querschnittsthema Strahlenforschung "Transportprozesse in Mensch und Umwelt", 24.-25.10.2017, Darmstadt, Deutschland

Publ.-Id: 26213 - Permalink


Liquid metal batteries
Weber, N.; Ashour, R.; Galindo, V.; Herreman, W.; Horstmann, G.; Kelley, D.; Köllner, T.; Landgraf, S.; Nimtz, M.; Nore, C.; Personnettaz, P.; Salas, A.; Starace, M.; Stefani, F.; Weier, T.;
The talk will give an overview on fluid dynamics in liquid metal batteries.
  • Invited lecture (Conferences)
    GDRI dynamo, 27.11.2017, Paris, Frankreich

Publ.-Id: 26212 - Permalink


Simulation and experimental verification of magnetic field induced proton dose enhancement effects
Lühr, A.; Burigo, L. N.; Gantz, S.; Schellhammer, S.; Hoffmann, A. L.;
Purpose/Objective
Proton therapy (PT) is expected to benefit greatly from integration with magnetic resonance (MR) imaging due to its sensitivity to anatomical variations. Consequently, the concept of MR-guided PT (MRPT) receives increased interest. Previous studies on MR-guided photon therapy (MRXT) have reported local dose enhancement of up to 40% at tissue-air interfaces caused by the electron return effect (ERE) in transverse magnetic fields. For MRPT, however, no consensus on the magnitude and hence the clinical effect of the ERE can be found in the scarcely available literature. The objectives of this study were 1) to confirm the ERE for PT by measurements and 2) to determine its magnitude for clinically relevant proton energies and MR field strengths by simulation.
Material/methods
Measurements were performed with a collimated 200 MeV proton beam traversing a PMMA phantom made of one or two 10 mm vertical slabs. Dose was measured with GafChromic EBT3 films (PMMA equivalent thickness 0.312 mm) using two experimental setups: (A) as reference, one film sandwiched between two slabs and (B) two films attached to the distal end of one slab, resulting in effective measurement depths of 10.156, 0.467, and 0.156 mm from the air interface. Film irradiations were performed under the same conditions without and within a transversal field (0.92 ± 0.02 T) of a permanent magnet. All measurements were repeated 4 to 8 times and the entire experiment was performed twice.
Monte Carlo simulations were performed using Geant4 (V 10.3). The proton beam shaping devices, magnetic field and PMMA slabs were modelled in detail. The EBT3 films were simulated as PMMA slabs and dose was scored in PMMA from 25 to 1000 μm distance to the air interface. Additionally, field strengths were varied between 0.35 and 1.5 T for a 210 MeV proton beam as well as proton energy between 90 and 210 MeV at 1 T. The dose enhancement ratio was defined as dose with divided by dose without magnetic field: DB/D.
Results
Significant dose enhancement was measured at the PMMA-air interface with magnetic field compared to no field (p<0.01) and confirmed by repeated experiments. The dose enhancement decreased with increasing distance from the interface (Fig. 1). Good agreement was achieved between measured and simulated dose both with and without magnetic field.
The dose enhancement ratio was largest in simulations with strong magnetic fields increasing from 2.0% in the presence of a 0.35 T field up to 7.4% for a 1.5 T field near the interface (Fig. 2). A decrease of the proton energy resulted in a decreasing dose enhancement ratio.
Conclusion
For the first time, the ERE for proton beams in a transverse magnetic field was demonstrated experimentally. The significant dose enhancement is predictable and limited to within 1 mm from the air interface for clinically relevant proton energies and magnetic field strengths.
Although smaller than for MRXT, the ERE may affect the clinical treatment of e.g. lung tumors.
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S317-S318

Publ.-Id: 26211 - Permalink


Robust optimization is not sufficient to account for anatomical changes in bilateral head and neck intensity-modulated proton therapy
Cubillos Mesias, M.; Troost, E.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.;
Purpose/Objective
Robust optimization in proton therapy considers uncertainties in patient setup and particle range during the plan optimization. In general, however, anatomical changes occurring during the treatment course, potentially causing a degradation of the plan quality, are neglected. The aim of this study was to quantify the influence of these changes on the dose distribution for patients with bilateral head and neck cancer (HNC).

Material/Methods
Datasets from 20 HNC patients, consisting of a planning CT and weekly control CTs (cCT), were analyzed. Intensity-modulated proton therapy (IMPT) plans with minimax robust optimization were calculated, accounting 3 mm and 3.5% for setup and range uncertainty, respectively. Prescribed doses to the low- and high-risk clinical target volume (CTV) were 57 and 70 Gy(RBE), respectively, delivered in 33 fractions. The organs at risk (OAR) spinal cord, brainstem, parotid glands, larynx, pharyngeal constrictor and esophageal inlet muscle were considered for plan optimization. Weekly cumulative doses, taking the anatomical variations of the cCTs into account, were compared with the nominal plan.
When a reduction in target coverage and/or increased dose to OARs was detected, a plan adaptation was performed on the cCT where the dose degradation was observed. Furthermore, for these patients an additional robust plan was calculated, taking also anatomical changes from the first two cCTs into account in the robust optimization. It was evaluated if a subsequent plan adaptation would still be necessary.

Results
Nominal plans fulfilled the clinical specifications of D98% ≥ 95% of the prescribed dose to the CTVs (range 96.58-98.81% for low-risk CTV and 96.83-98.76% for high-risk CTV). During the treatment course, anatomical changes lead to reduced weekly cumulative D98% values in five patients (25%; minimum 90.17% for low-risk CTV and 89.19% for high-risk CTV). Doses in OARs remained below the clinical constrains during the treatment course. One treatment adaptation was performed for each of these five patients, which allowed a target coverage improvement (range 97.68-99.72% for low-risk CTV and 95.89-98.46% for high-risk CTV). Total cumulative doses including adaptation were acceptable (range 96.67-98.37% for low-risk CTV and 95.11-97.39% for high-risk CTV, see Figure 1a).
The results for the more sophisticated robust plan, considering the first two cCTs, were diverse: whereas plan adaption became obsolete in one patient, the total cumulative dose would, without adaptation, still have been below clinical constraints in another (Figure 1b and 2).

Conclusion
In a substantial number of patients, robust optimization only is not sufficient to account for anatomical changes occurring during the treatment course, resulting in severe target coverage degradation. Assessment of the cumulative weekly doses allowed detection of target coverage loss. The importance of frequent in-treatment imaging is underlined.
Keywords: robust optimization, treatment adaptation, proton therapy
  • Lecture (Conference)
    ESTRO 37, 20.-24.04.2018, Barcelona, España
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S271-S272
    DOI: 10.1016/S0167-8140(18)30827-2

Publ.-Id: 26210 - Permalink


First in-beam MR scanner for image-guided proton therapy: beam alignment and magnetic field effects
Schellhammer, S. M.; Karsch, L.; Smeets, J.; L'Abbate, C.; Henrotin, S.; van der Kraaij, E.; Lühr, A.; Quets, S.; Pawelke, J.; Hoffmann, A.;
Purpose/Objective
Although proton therapy is expected to greatly benefit from integration with magnetic resonance (MR) imaging for on-line image guidance, to date such integration has not been realized. Both the MR scanner’s static (B0) and gradient magnetic fields may compromise beam quality. The aim of our study was 1) to align the field-of-view (FOV) of an MR scanner with a horizontal fixed proton beam line and 2) to assess the effects of the scanner’s B0 and gradient fields on the beam.

Material/methods
Beam alignment: An open MR scanner (MRJ2200, Paramed) featuring a 0.22 T vertical magnetic field was mounted on a trolley and RF-shielded by a compact Faraday cage (Fig. 1). To ensure that the beam traverses the scanner’s magnetic isocentre for beam energies between 70 and 230 MeV, the Lorentz-force induced beam deflection was predicted by Monte Carlo (Geant4) simulations based on Hall probe (HHP-VU, Arepoc) based mapping of the scanner's B0 field. The magnetic isocentre of the scanner was marked by the overlapping gradient fields being visible as dark crosses in 3 orthogonal slices using an MR imaging phantom (ACR Small Phantom). The proton beam was collimated to Ø10 mm and localized in the FOV by radiochromic film (Gafchromic EBT3, Ashland) affixed vertically to the phantom’s front.
Beam quality assessment: With Faraday cage removed, beam profiles were acquired with and without MR scanner for 72, 125 and 219 MeV beams using a pixelated scintillation detector (Lynx, IBA Dosimetry) positioned at 220 cm from the beam exit window. These measurements were repeated while performing spin echo and gradient echo sequences (gradient up to 5.7 mT/m). Planar dose distributions of 72 and 125 MeV beams were measured at the scanner’s FOV with films placed horizontally between two PMMA slabs.

Results
Beam alignment: As a mean lateral deflection of 2 cm was predicted at the magnetic isocenter, the scanner was laterally displaced by 2 cm from the beam’s central axis. The dose distribution on the vertically oriented film confirmed a proper alignment of the beam and the FOV. Thus, the scanner's position was fixed and a cylindrical beam guide was installed into the Faraday cage at beam entrance.
Beam quality assessment: On the scintillation detector, the beam showed a horizontal deflection of 22, 16 and 11 cm for 72, 125 and 219 MeV, respectively, and a vertical deflection below 0.6 mm. The horizontal deflection was taken into account for installing a beam stopper, while vertical deflection was considered negligible. The beam profiles were not affected by the gradient fields of the sequences. Planar film measurements showed curved beam paths with a lateral Bragg peak displacement of 2 and 5 mm for 72 and 125 MeV, respectively (Fig. 2).

Conclusion
Alignment of an open MR scanner’s FOV with a horizontal fixed proton beam has been realized taking into account the scanner’s B0 field induced beam deflection. Sequence-dependent gradient fields do not affect the beam profile.
  • Lecture (Conference)
    ESTRO 37 - Annual Meeting of the European Society for Radiotherapy & Oncology, 20.-24.04.2018, Barcelona, Espana
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S318-S319
    DOI: 10.1016/S0167-8140(18)30915-0

Publ.-Id: 26209 - Permalink


Chemische Effekte bei Kühlmittelverluststörfällen in Druckwasserreaktoren - Arbeiten des Kompetenzzentrums Ost für Kerntechnik
Kryk, H.; Kästner, W.; Hampel, U.; Seeliger, A.;
Zur Abfuhr der Nachzerfallswärme in der Spätphase eines Kühlmittelverluststörfalles in Druckwasserreaktoren wird das aus den Leck im Primärkreislauf austretende Kühlwasser aus dem Reaktorsumpf im sog. Sumpfumwälzbetrieb mittels der Niederdruckeinspeisepumpen in den Reaktorkern rezirkuliert. Im Containment kommt das Kühlmittel dabei in Kontakt mit Fremdstoffen, wie z.B. Isoliermaterialfasern, Staub und korrosiven Materialien, welche einerseits die Kühlmittelchemie und andererseits die Performance der den Pumpen vorgeschalteten Sumpfsiebe beeinflussen können. Weiterhin haben Studien gezeigt, dass feuerverzinkte Containment-Einbauten (z.B. Lichtgitterroste, Stützgitter von Sumpfsieben, Kanäle) einer beschleunigten Korrosion durch das borsäurehaltige Kühlmittel unterliegen. Die daraus resultierenden thermohydraulischen Effekte hängen in hohem Maße vom Löslichkeitsverhalten der Korrosionsprodukte ab. So können unlösliche Korrosionspartikel zu einem erhöhten Differenzdruck an den bereits mit Isoliermaterialfasern beladenen Sumpfsieben führen, während lösliche Korrosionsprodukte nicht zurückgehalten werden und somit in den Kern gelangen, was unter Umständen in Ausfällungsprozessen durch Temperaturänderungen resultiert.
Da ein Einfluss dieser Effekte auf die Kernkühlung nicht ausgeschlossen werden kann, ist die Untersuchung der zugrundeliegenden physikochemischen Korrosions-, Ausfällungs- und Ablagerungsprozesse sowie deren thermohydraulischen Folgen Gegenstand von gemeinsamen Forschungsvorhaben des Helmholtz-Zentrums Dresden-Rossendorf, der TU Dresden sowie der Hochschule Zittau-Görlitz. Der Vortrag gibt einen Überblick über die bisherigen Forschungsarbeiten der o.g. Institutionen sowie die wesentlichen Ergebnisse der entsprechenden BMWi-Forschungsvorhaben im Kontext der Reaktorsicherheitsforschung.
Keywords: Kühlmittelverluststörfall, KMV, Druckwasserreaktor, DWR, Korrosion, Zink, Zinkborat, Reaktorsicherheitsforschung, Loss-of-coolant Accident, LOCA, Pressurized Water Reactor, PWR, Corrosion, Zinc, Zinc Borate, Nuclear Safety Research, Chemical Effects
  • Invited lecture (Conferences)
    49. Kraftwerkstechnisches Kolloquium 2017, 17.-18.10.2017, Dresden, Deutschland
  • Contribution to proceedings
    49. Kraftwerkstechnisches Kolloquium 2017, 17.-18.10.2017, Dresden, Deutschland
    Kraftwerkstechnik 2017 - Strategien, Anlagentechnik und Betrieb, Freiberg: SAXONIA, 978-3-934409-79-8, 101-115

Publ.-Id: 26208 - Permalink


Combining different genomic signatures to improve the predictive power for LRC after PORT-C in HNSCC
Schmidt, S.; Linge, A.; Zwanenburg, A.; Leger, S.; Großer, M.; Lohaus, F.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Belka, C.; Combs, S. E.; Mönnich, D.; Zips, D.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.; Löck, S.;
Purpose: To improve compare and improve the performance of a hypothesis-driven 7-gene signature by with a signature based on whole transcriptome analysis for the prognosis of loco-regional tumour control (LRC) in patients with HPV-negative locally advanced head and neck squamous cell carcinoma (HNSCC) after postoperative radiochemotherapy (PORT-C).

Material and methods: Gene expression analyses were performed on a multicentre retrospective cohort of 125 patients with HPV16 DNA negative HNSCC using the GeneChip® Human Transcriptome Array 2.0 (Affymetrix) for whole transcriptome analysis. To identify a gene signature prognostic for LRC from the whole transcriptome data, 3085 genes were considered, which previously have been related to radioresistance or response to radiotherapy [1-4]. The final gene signature was based on the comparison of different signature sizes, feature selection algorithms and prognostic models. The performance of the whole transcriptome-based signature was compared to a previously identified 7-gene signature based on nanoString analysis of a hypothesis-driven gene set containing 171 genes, using the concordance index (ci). The signatures were applied independently and combined to stratify patients into groups of low (LR) and high (HR) risk of recurrence.

Results: The identified gene signatures based on whole transcriptome data showed improved performance (ci 0.79-0.87) compared to the signatures based on the hypothesis-driven gene set (0.72-0.78). The model with the best performing gene signature contained genes related to tumourigenesis, invasion, cell cycle regulation and immune response. Patient stratification into low and high risk groups was performed for both signatures, see figures (A) and (B). The difference in LRC between both groups was highly significant (p<0.001). Compared to the 7-gene nanoString signature, the LR group showed a slightly improved LRC for the Affymetrix signature, similar to that of HPV positive tumours. Finally, a combined high risk group was defined, including patients who were classified as high risk patients by both gene signatures. This patient group showed a poor LRC of only about 45% compared to the individual signatures, see figure (C).

Conclusion: We determined a gene signature predicting LRC in a cohort of 125 HPV16 DNA negative HNSCC patients after PORT-C based on whole transcriptome analysis.
This signature showed improved performance compared to the 7-gene signature identified on a limited hypothesis-driven gene set, indicating that the inclusion of additional genes during feature selection may lead to a better performing signature.s may further enhance this signature.
The combination of both models allowed for the identification of a patient group with HPV-negative HNSCC who are on a particularly high risk of developing a recurrence, and may be considered for future dose-escalation trials.
Keywords: Head and neck squamous cell carcinoma, Genomics, Machine Learning, HNSCC, Cancer, Radiotherapy
  • Lecture (Conference)
    ESTRO 37, 20.-24.04.2018, Barcelona, Spanien
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S140-S141
    DOI: 10.1016/S0167-8140(18)30586-3

Publ.-Id: 26207 - Permalink


Research Data Management to increase research quality
Konrad, U.;
The publication is an invited plenary lecture at the national workshop on documentation and information in Jakarta, Indonesia.
Research data play a fundamental role in todays open science driven research. In addition the software used to generate, process or analyse the data has to be considered for the whole research and publication process to ensure, that results are findable, accessible, interoperable, re-usable and re-producible. The lecture describes the challenges, tasks, solutions and organization structures to meet the challenges for the library and data center at the Helmholtz-Center Dresden-Rossendorf and beyond.
Keywords: Open Science, Research Data Management, Software Management, Data Center, Library
  • Invited lecture (Conferences)
    National Workshop on Documentation and Information Data, Information and Knowledge, 25.-26.10.2017, Jakarta, Indonesia
    DOI: 10.5281/zenodo.1040289

Downloads:

Publ.-Id: 26206 - Permalink


Characterization of in-beam MR imaging performance during proton beam irradiation
Hoffmann, A.; Gantz, S.; Grossinger, P.; Karsch, L.; Pawelke, J.; Serra, A.; Smeets, J.; Schellhammer, S.;
Purpose/Objective
Given the sensitivity of proton therapy (PT) to anatomical changes, it could greatly benefit from integration with magnetic resonance (MR) imaging. Hence, there is growing interest to investigate the technical feasibility of MR-integrated proton therapy (MRiPT). The aim was to operate an MRI system in the beam of a PT facility and to characterize the MR imaging performance during simultaneous irradiation.

Material and Methods
A 0.22 T open MR scanner (MrJ2200, Paramed Medical Systems) was installed in a compact Faraday cage at the fixed horizontal beamline of our PT facility. A beam guide in the wall of the cage allows beam transmission to the field-of-view (FOV) of the scanner. The scanner’s magnetic isocenter was aligned, such that a 10 mm diameter collimated proton beam of 125 MeV was stopped in the most distal image slice of the ACR Small Phantom, which was centrally positioned in the FOV inside a dedicated knee coil. Prior to irradiation, the magnet was shimmed and the magnetic field homogeneity (MFH) was mapped over a 22 cm diameter spherical volume by a magnetic field camera (MFC3045, Metrolab). To assess the effect of magnetic fringe fields of the nearby beam line magnets, the MFH measurements were repeated while these magnets were energized for beam energies between 70-220 MeV. During irradiation, the phantom was imaged using T1 and T2-weighted spin echo (SE) sequences with parameter settings according to the phantom test guidance from the ACR. Additionally, two gradient echo (GRES and GREL) scans were performed with a short repetition time (TR) and long echo time (TE): TR = 30 and 80 ms, and TE = of 8 and 30 ms, respectively, a flip angle of 20 deg and acquired voxel size of 0.63x0.79x5.00 mm3. A validated software tool (MATLAB) was used to extract the ACR imaging parameters and to estimate a geometric transformation from image pairs with and without beam.

Results
After shimming, the peak-to-peak MFH was 88 ppm, which is within the scanner’s operating specifications. The MFH measurements with and without energized beam line magnets show no significant differences, but the baseline resonance frequency was increased by 70-110 Hz depending on beam energy. The SE and GRE image quality was sufficient for analysis. Differences in ACR parameters due to operating the beam line magnets or the beam were within measurement uncertainties. A sequence-dependent translation of 0.5-3 mm in frequency encoding direction was observed in the images due to empowering of the beam line magnets, with GREL being the most sensitive sequence.

Conclusion
No degradation of the performance of the in-beam MR system was found during simultaneous operation with the PT system. Although MR imaging during irradiation does not deteriorate the ACR parameters, there is a sequence-dependent off-resonance image displacement when the beam line magnets are energized. This proof-of-concept justifies further research towards the development of a first prototype for MRiPT.
Keywords: MR imaging, proton therapy, image quality

Publ.-Id: 26205 - Permalink


Novel concept to personalize radiation oncology: Predicting cell-specific survival prior to treatment
Oesten, H.; von Neubeck, C.; Jakob, A.; Loeck, S.; Enghardt, W.; Krause, M.; Mcmahon, S. J.; Grassberger, C.; Paganetti, H.; Lühr, A.;
(1) Purpose/Objective
To enhance tumor response and thus treatment outcome in radiation therapy, a dose prescription strategy prior to treatment is necessary to individualize radiation oncology.
However, prediction of cell-specific survival prior to treatment is currently unavailable. Thus, we developed an approach to stratify patients prior to therapy by predicting individual radiation response based on cell survival.

(2) Material/methods
Based on a previously developed mechanistic radiation response model of DNA repair and cell survival (S_cell) prediction for normal tissue cells, we simulated measured ∝- and β-values of 19 in vitro cancer cell lines (skin, lung, brain). The radiation model incorporates four cell-specific parameters: number of chromosomes, p53-mutation-status, cell-cycle distribution and the effective genome size (eGS). The first three are only experimentally available; the latter was obtained through minimizing the difference between the simulated and measured ∝- and β-values. A parametrization of eGS as a function of the cells’ chromosome number was proposed. The correct choice of all parameters was validated by an independent dataset of time-dependent γ-H2AX data over 24h.

(3) Results
Overall good agreement between simulated and measured in vitro cancer S_cell curves was achieved (Fig. 1). The measured β values were found to increase quadratically with the obtained eGS (R^2=0.81) irrespectively of other cell-specific parameters (Fig. 2b). The measured ∝ values increased linearly with the eGS manifesting different slopes distinguishable into the cells’ p53-mutation-status (Fig. 2a). Measured ∝ and β were predictable based on eGS with an uncertainty of one sigma: σ=0.04Gy^(-1) for ∝ and σ=0.01Gy^(-2) for β. The eGS was found to correlate (R^2=0.70) with the number of chromosomes for all but four cell lines. The detailed cell-specific cell cycle distributions were found to have a negligible impact on the radiobiological parameters. Measured time-dependent γ-H2AX data was predictable through repair kinetics simulations.

(4) Conclusion
A mechanistic model for radiation response of normal human cells was successfully modified to allow for simulations of measured in vitro S_cell of 19 cancer cell lines. Independent of cancer entity, the radiobiological value β was predictable only by the eGS while the prediction of ∝ required in addition at least knowledge of the p53-mutation-status. An enhanced correlation of the eGS with a clinically accessible parameter, as suggested, may facilitate a stratification strategy based on cell-specific survival prediction for individualized patient treatment in radiotherapy.
  • Lecture (Conference)
    ESTRO 37 - Innovation for Value and Access, 20.-24.04.2018, Barcelona, Spanien

Publ.-Id: 26204 - Permalink


Population balance modeling using class and quadrature-based moment methods with application to bubbly flows
Oertel, R.; Li, D.; Pollack, M.; Saalenbauch, S.; Schlegel, F.; Hasse, C.; Lucas, D.;
Multi-phase flows with a continuous and a distinct disperse phase are essential in a variety of industrial applications, e.g., in chemical engineering or in nuclear safety research. These flows are usually polydisperse, i.e., the disperse phase exhibits a size distribution. In case of bubbly flows, the size distribution and its statistical moments are highly influenced by the overall heat- and mass transfer rates as well as the flow structure, e.g., during the transition from the homogeneous to the heterogeneous regime in bubble columns. Temporal and spatial changes of the size distribution can be described with a transport equation for the number density function (NDF), i.e., the population balance equation (PBE). Two popular Eulerian methods to solve the PBE are the method of classes and the family of Quadrature Based Methods of Moments (QBMM). Both approaches have been applied in CFD before, e.g., for simulations of stirred tanks, spray behavior or soot formation. However, OpenFOAM offers no capabilities in this regard. While the Quadrature Method of Moments (QMOM) - the basic QBMM approach - tracks only the moments of the NDF, class methods track the shape of the NDF directly by means of discretization. An extended version of QMOM, called EQMOM, allows reconstructing the NDF using a set of kernel density functions. All three approaches are implemented into the OpenFOAM library and validated against analytical solutions. A comparison for pipe flow and bubble column cases using appropriate coalescence and breakup models shows the accuracy and performance of each method. Furthermore, it is known for bubbly flows that the velocity of the disperse phase is generally size dependent and the bubbles may separate spatially. An extreme case is the lift force, which governs the lateral migration of bubbles in a liquid shear field and changes its sign at a critical diameter. This effect is not covered by the general two-fluid or Euler-Euler approach. Partially, this can be taken into account using a multi-fluid solver, by splitting the disperse phase into velocity groups with fixed boundaries. An alternative approach is to include the velocity as an internal coordinate into the PBE, which gives the generalized PBE (GBPE). Using a size-conditioned velocity approach, the GBPE can be solved within the QBMM framework. Thereby, a continuous information about the dependency of velocity on size can be obtained. The work presents first results and comparisons between the two approaches.
  • Invited lecture (Conferences)
    5th OpenFOAM User Conference, 17.-18.10.2017, Wiesbaden, Deutschland

Publ.-Id: 26203 - Permalink


Markers from Australia’s nuclear legacy in marine wildlife
Hotchkis, M.; Child, D.; Johansen, M. P.; Collins, R. N.; Howell, N.; Howard, D. L.; Ikeda-Ohno, A.ORC
Accelerator Mass Spectrometry (AMS) provides a high-sensitivity method for detection of long-lived radioisotopes. New facilities at ANSTO’s Centre for Accelerator Science are enabling us to detect plutonium by AMS with unprecedented level of sensitivity. We can now detect traces of the isotope 244Pu (half-life 80 million years) which arrive on earth on interstellar dust. However, the predominant source of plutonium on earth’s surface is from human activities, in particular from atmospheric nuclear testing of the 1950-1960’s. In Australia, the radiological residues originating from the British tests at the Montebello Islands, WA, occur in distinct isotopic and morphologic forms. The three tests had slightly different Pu isotopic signatures. Today, aided by the high sensitivity of AMS, their distinct 240/239Pu atom ratios can be differentiated in biological samples, such as failed sea turtles eggs gathered from beaches. Local fish tend to reflect a mixture of all three tests due to the movement of the fish and transport of Pu by water currents. On a larger scale, the 240/239Pu atom ratios in all samples (median ratio 0.04) are distinct from worldwide fallout (0.17-0.18) and can be used as a tracer for migrating species. The Pu exists in the environment in the form of ‘hot’ particles; the mobility of these particles and their availability for uptake into living organisms depends on their physical and chemical characteristics, which we are currently studying using a range of methods including synchrotron-based X-ray fluorescence microscopy (XFM).
Keywords: Nuclear tests, radioactive contamination, environment, plutonium, AMS, synchrotron, XFM
  • Lecture (Conference)
    ANSTO User Meeting, 22.-24.11.2017, National Centre for Synchrotron Science, Melbourne, Australia

Publ.-Id: 26202 - Permalink


Sb-related defects in Sb-doped ZnO thin film grown by pulsed laser deposition
Luo, C.; Ping, H. L.; Azad, F.; Anwand, W.; Butterling, M.; Wagner, A.; Kuznetsov, A.; Zhu, H.; Su, S. C.; Ling, F. C. C.;
Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by the Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ~8×E20 cm-3, the as-grown films grown with appropriate oxygen pressure could be n~4×E20 cm-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples lead to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.
Keywords: ZnO, Sb-doping, shallow donors, shallow acceptors, compensating defects

Publ.-Id: 26200 - Permalink


Magnetohydrodynamic flow simulation in liquid metal batteries
Weber, N.; Personnettaz, P.; Stefani, F.; Weier, T.;
Overview about numerical simulation of liquid metal batteries at HZDR
  • Lecture (Conference)
    OpenFuelCell Workshop, 24.10.2017, Forschungszentrum Jülich, Deutschland

Publ.-Id: 26199 - Permalink


Radionuklide in der Biosphäre - molekulare Wechselwirkung mit Mikroorganismen
Raff, J.;
Im Rahmen des Vortrags wird anhand von verschiedenden Organismen wie Algen, Bakterien und Pilzen erläutert, wie Mikroorganismen mit Radionukliden interagieren und welche Konsequenzen diese Wechselwirkung für das Migrationsverhalten von Radionukliden in der Umwelt hat.
Keywords: Mikroorganismen, Radionuklide, Wechselwirkungen, Migration
  • Invited lecture (Conferences)
    2. Workshop – Helmholtz Cross Program Activity Querschnittsthema Strahlenforschung „Transportprozesse in Mensch und Umwelt", 24.-25.10.2017, Darmstadt, Deutschland

Publ.-Id: 26198 - Permalink


Radionuclides in living organisms – Calorimetric determination of the radionuclide toxicity
Sachs, S.; Fahmy, K.ORC; Oertel, J.; Geipel, G.; Bok, F.
Quantification of radionuclide transfer within the environment and to the food chain is required for the reliable human risk assessment. The uptake of radionuclides by plants is typically described phenomenologically by transfer factors. However, investigations on a molecular level are necessary to understand the underlying processes. We studied the interaction of U(VI) with canola cells (Brassica napus) focusing on the concentration-dependent impact of U(VI) on the cell metabolism. Isothermal microcalorimetry was used to monitor the metabolic heat flow of the cells, which was compared to the cell viability. The speciation of U(VI) in the medium was determined by time-resolved laser-induced fluorescence spectroscopy and thermodynamic modeling. The data reveal the correlation of U(VI) hydroxo species with metabolic heat release and general oxidoreductase on a quantitative toxicity scale [1].

[1] Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K., Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Env. Sci. Technol. 51 (2017) 10843.
Keywords: plant cells, uranium, cell metabolisms, isothermal microcalorimetry, cell viability, speciation, TRLFS, thermodynamic modeling, speciation
  • Invited lecture (Conferences)
    2. Workshop - Helmholtz Cross Program Activity, Querschnittsthema Strahlenforschung "Transportprozesse in Mensch und Umwelt", 24.-25.10.2017, Darmstadt, Deutschland

Publ.-Id: 26197 - Permalink


Ultra-high-speed X-ray imaging of laser-driven shock compression using synchrotron light
Olbinado, M. P.; Cantelli, V.; Mathon, O.; Pascarelli, O.; Rack, A.; Grenzer, J.; Pelka, A.; Roedel, M.; Prencipe, I.; Garcia, A. L.; Helbig, U.; Kraus, D.; Schramm, U.; Cowan, T.; Scheel, M.; Pradel, P.; de Resseguier, T.;
A high-power, nanosecond-pulsed laser impacting the surface of a material can generate an ablation plasma that drives a shock wave into it; while in situ X-ray imaging can provide a time-resolved probe of the shock-induced material behaviour on macroscopic lengths scales. Here, we report on an investigation into laser-driven shock compression of a polyurethane foam and a graphite rod by means of single-pulse synchrotron X-ray phase-contrast imaging with a MHz frame rate. A 6-J, 10-ns-pulsed laser was used to generate shock compression. Physical processes governing the laser-induced dynamic response such as elastic compression, compaction, pore collapse, fracture, and fragmentation have been imaged; and the advantage of exploiting the partial spatial coherence of a synchrotron source for studying low-density, carbon-based materials is emphasized. The successful combination of a high-energy laser and ultra-high-speed X-ray imaging using synchrotron light demonstrates the potentiality of accessing complementary information from scientific studies of laser-driven shock compression.
Keywords: laser shock, ultra-high-speed imaging, synchrotron radiation, X-ray phase contrast, time-resolved studies, foam, graphite, shock

Publ.-Id: 26196 - Permalink


Enzymatic Decolourization of Water Using Loofa Sponge as Cellular Carrier: Immobilization and Dye Degradation Performance
Mohammed, I.; Werner, A.; Schubert, M.; Hampel, U.;
In recent years, strong efforts have been made to develop sustainable biocatalytic decolorization processes for dye-polluted water. In particular, dye-oxidizing laccase enzymes immobilized on suitable carriers are promising candidates, which can be reused as long as the activity is sufficiently high.
In this work, we propose, for the first time, a new methodology to immobilize laccase from Trametes hirsute on natural-grown and decomposable cellular loofa sponge carrier and assess the capability to degrade dye-polluted water. High immobilization activity is achieved and about 70 % residual activity remains after 8 cycles. Additionally, we determined homogenous and heterogeneous kinetic parameters for free and immobilized enzymes. Results reveal four times higher Michaelis-Menten constant of the laccase immobilized on loofa due to mass transfer and mixing limitations in packed bed bio-reactor.
Eventually, the response surface methodology was applied to identify favorable operation condition in terms of dye concentration, treatment time and mixing velocity. Here, the results demonstrated a remarkable dye removal capability with shorter treatment time compared to the previous studies on immobilized laccase reported in the literature.
Keywords: Laccase, Enzymatic decolorization, Loofa sponge, Immobilization, activity analysis, Response surface methodology

Publ.-Id: 26195 - Permalink


Observation of ultrafast solid-density plasma dynamics using femtosecond X-ray pulses from a free-electron laser
Kluge, T.; Rödel, M.; Metzkes, J.; Bussmann, M.; Erbe, A.; Galtier, E.; Garcia, A. L.; Garten, M.; Georgiev, Y. M.; Gutt, C.; Hartley, N.; Huebner, U.; Lee, H. J.; Mcbride, E. E.; Nakatsutsumi, M.; Nam, I.; Pelka, A.; Prencipe, I.; Rehwald, M.; Christian, R.; Schönherr, T.; Zacharias, M.; Zeil, K.; Glenzer, S.; Schramm, U.; Cowan, T. E.;
The complex physics of the interaction between short pulse high intensity lasers and solids is so far hardly accessible by experiments. As a result of missing experimental capabilities to probe the complex electron dynamics and competing instabilities, this impedes the development of compact laser-based next generation secondary radiation sources, e.g. for tumor therapy, laboratory-astrophysics, and fusion. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that Small Angle X-ray Scattering (SAXS) of femtosecond X-ray free-electron laser (XFEL) pulses facilitates new capabilities for direct in-situ characterization of intense short-pulse laser plasma interaction at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short pulse high intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the pre-inscribed grating, due to plasma expansion, which is an hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets.
  • Open Access LogoPhysical Review X 8(2018), 031068
    DOI: 10.1103/PhysRevX.8.031068
  • Lecture (Conference)
    59th Annual Meeting of the APS Division of Plasma Physics, 23.-27.10.2017, Milwaukee, USA
  • Lecture (Conference)
    10th International Conference on Inertial Fusion Sciences and Applications, 11.-12.09.2017, Saint Malo, Frankreich

Publ.-Id: 26194 - Permalink


Competing forces in liquid metal electrodes and batteries
Ashour, R.; Kelley, D.; Salas, A.; Starace, M.; Weber, N.; Weier, T.;
Liquid metal batteries have been proposed for low-cost grid scale energy storage. During their operation, solid intermetallic phases often form in the cathode and are known to limit the efficiency of the cell. Fluid flow in the liquid electrodes can enhance mass transfer and reduce or avoid the formation of intermetallics, and fluid flow can be promoted by careful choice of the locations and topology of a battery’s electrical connections, which affect the thermal buoyant forces and electromagnetic forces acting on the electrodes. In this context we study four phenomena that drive flow: Rayleigh-Bénard convection, internally heated convection, electro-vortex flow, and swirl flow, in both experiment and simulation. In experiments, we use ultrasound Doppler velocimetry (UDV) to measure the flow of an electrode made of liquid eutectic PbBI at 160 ◦ C and subject to all four phenomena. In numerical simulations, we isolate the phenomena and simulate each separately using OpenFOAM. Comparing simulated velocities to experiments via a UDV beam model, we find that all four phenomena can enhance mass transfer in LMBs. We explain the flow direction and structure, and give estimates for the magnitude of the mean velocity depending on the cell current. We describe how the phenomena interact and propose dimensionless numbers for estimating their mutual relevance. A brief discussion of electrical connections summarizes the engineering implications of our work.

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  • Secondary publication expected

Publ.-Id: 26193 - Permalink


In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon
Tokel, O.; Turnalı, A.; Makey, G.; Elahi, P.; Çolakoğlu, T.; Ergeçen, E.; Yavuz, Ö.; Hübner, R.; Zolfaghari Borra, M.; Pavlov, I.; Bek, A.; Turan, R.; Koray Kesim, D.; Tozburun, S.; Ilday, S.; Ilday, F. Ö.;
Silicon is an excellent material for microelectronics and integrated photonics, with untapped potential for mid-infrared optics. Despite broad recognition of the importance of the third dimension, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements, electronic devices and better electronic–photonic integration are lacking. Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-μm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface - that is, ‘in-chip’ - microstructures for microfluidic cooling of chips, vias, micro-electromechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.

Publ.-Id: 26192 - Permalink


Nanomagnet fabrication by ion beams
Fassbender, J.;
In recent years the tailoring of magnetic properties by means of ion irradiation and implantation techniques has become fashionable. Early investigations relied on the fact that the perpendicular magnetic anisotropy of Co/Pt multilayers depend sensitively on the interface sharpness [1]. Subsequently also the ion induced modification of exchange bias phenomena as well as interlayer exchange coupling have been investigated [2]. For single magnetic films ion implantation has been used to reduce the Curie temperature and hence the saturation magnetization [3]. Nowadays also the reverse process, i.e. the creation of nanomagnets within special binary alloys is employed [4,5]. In combination with lithography or with focused ion beams a pure magnetic patterning becomes possible [6] leading to hybrid magnetic materials [7] with properties different from both, the ion irradiated as well as the untreated material. Even ion induced chemical reduction can be employed to create a nanomagnetic pattern [8,9].
An overview of the present status in this research field will be given.
[1] C. Chappert et al., Science, 280 (1998) 1919.
[2] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D, 37 (2004) R179. [3] J. Fassbender, J. McCord, Appl. Phys. Lett., 88 (2006) 252501.
[4] E. Menendez et al., Small, 5 (2009) 229.
[5] R. Bali et al., Nano Lett., 14 (2014) 435.
[6] J. Fassbender and J. McCord, J. Magn. Magn. Mater., 320 (2008) 579. [7] J. McCord, L. Schultz, J. Fassbender, Adv. Mater., 20 (2008) 2090.
[8] S. Kim et al., Nature Nanotechnology, 7 (2012) 567.
[9] J. Fassbender, Nature Nanotechnology, 7 (2012) 554.
Keywords: magnetism, ion irradiation, magnetic patterning
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Publ.-Id: 26191 - Permalink


Gefüge und Eigenschaften des warmfesten Chromstahls P91
Kohlar, S.;
Aufgabenstellung:
Aus einem Rohrstück des Materials P91 soll nach der Erarbeitung eines Probenplans zunächst das Gefüge in allen 3 Orientierungen metallographisch charakterisiert werden. Anschließend wird das Material mechanisch - technologisch sowie bruchmechanisch und fraktographisch untersucht. Die daraus erhaltenen Werkstoffkennwerte sollen mit dem Gefüge und dem fraktographischen Befund in Beziehung gesetzt werden.
Großer Beleg, angefertigt 2009
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-082 2017

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Publ.-Id: 26190 - Permalink


Beschleunigertechnologie und Forschung am ELBE - Zentrum für Hochleistungsstrahlenquellen
Justus, M.;
Das ELBE - Zentrum für Hochleistungsstrahlenquellen ist die größte Nutzer-Forschungsanlage des Helmholtz-Zentrums Dresden-Rossendorf (HZDR). Mit dem 40 MeV -Elektronenbeschleuniger werden Wissenschaftlern mit Hilfe von Freie-Elektronen-Lasern, Terahertz-Quellen und Festkörper-Targets verschiedenen Arten von Sekundärstrahlung für interdisziplinäre Grundlagenforschung angeboten. Im Vortrag werden Grundlagen zur Beschleunigerphysik vermittelt und die Bedeutung von Teilchenbeschleunigern für die Forschung aufgezeigt. Anhand von supraleitender Beschleunigertechnik, Freie-Elektronen-Laser, Strahldiagnostik und Kontrollsystemen werden technologischen Herausforderungen und Lösungen für den Betrieb des Elektronenbeschleunigers erläutert. Außerdem werden einige Forschungsergebnisse aus ELBE-Nutzerexperimenten vorgestellt.
  • Lecture (others)
    Wissenschaftliches Seminar, 12.12.2017, Dresden, Deutschland

Publ.-Id: 26189 - Permalink


3D motion validation with clinically used cine-MRI and a MR-LINAC phantom
Dolde, K.; Schneider, S.; Pfaffenberger, A.; Hoffmann, A. L.;
Purpose/Objective:
Magnetic resonance (MR)-guided radiotherapy shows high potential to improve the precision and accuracy of radiation therapy. Especially hybrid MR-LINAC devices provide the possibility to perform on-line MR imaging during dose delivery and offer efficient tumour tracking or gating techniques for high-precision treatment of moving tumours. For the commissioning of such systems, the accuracy and reliability of real-time motion tracking through MR-imaging needs to be assessed. In this study we evaluate the dynamic target localization accuracy of a programmable MRI-compatible motion phantom using clinical cine-MRI sequences in all three spatial dimensions.
Material/Methods:
The phantom (CIRS Model 008M MRI-LINAC Dynamic Phantom) has a body representing a human thorax in shape and proportion that was filled with a 6,61g/l NaCl water solution. It incorporates an off-centric cylindrical rod with embedded gel-based target that can be moved and rotated through a programmable actuator. Sinusoidal motion trajectories with patient-oriented breathing frequencies (0.1-0.2 Hz) and motion amplitudes (5 mm – 20 mm) in all three spatial dimensions were programmed in the phantom’s Motion Control Software. Balanced steady-state free procession sequences (TE/TR=2.3/4.6 ms; FOV=300×300×150 mm³; Res=1.34х1.34 mm², SliceThickness=7 mm, FA=30°) were acquired in cine mode on a 3T MR scanner (Philips Achieva) with a time resolution of 489 ms. The center-of-mass motion of the target was extracted from the cine images using a manual segmentation-based procedure. Both the measured frequency and amplitude were compared to the programmed motion parameters. The frequencies were determined with a Fast Fourier Transform (FFT). The phantom was also fed with a real patient’s 1D-navigator-based breathing pattern to evaluate the accuracy of non-regular target motion detection.
Results:
The frequencies (f) and amplitudes (A) extracted from the cine-MRI are in good agreement to the pre-set values. For the sinusoidal motion patterns, we observed 2% deviations between the measured and pre-set frequencies in IS direction for f=0.1 Hz and f=0.2 Hz with A=20 mm. In AP and LR direction the frequency deviation is 3% for f=0.2 Hz and A=5 mm. The amplitudes were determined with a precision of 99% in IS, and 92% in AP/LR direction with deviations smaller than 0.4 mm. For the real patient’s navigator breathing-pattern with main frequency components between 0.14-0.2 Hz and amplitudes between 5-20 mm we observed an amplitude accuracy of 98% with a maximum deviation of 1.2 mm in IS direction. The uncertainties in frequency and amplitude are dominated by the spatial and time resolution.
Conclusion:
The study shows motion parameters of the MRI-LINAC Phantom to be extracted from cine-MRI with high accuracy. Dynamic target localization through cine-MRI is feasible and accurate for the management of respiratory motion in radiation oncology.
Keywords: Intrafractional Motion Management - Tracking
  • Poster
    Estro 37, 20.04.2018, Barcelona, Spain
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S511-S512
    DOI: 10.1016/S0167-8140(18)31251-9

Publ.-Id: 26188 - Permalink


Nanoscale imaging and compositional analysis in the helium ion microscope
Klingner, N.ORC; Heller, R.; Hlawacek, G.; Möller, W.; Facsko, S.
Ongoing miniaturization in semiconductor industry, nanotechnology and life science demands further improvements for high-resolution imaging, fabrication and analysis of the produced nanostructures. Continuously shrinking object dimensions led to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques.
Ion beam analysis performed on nanometer scale may comply with this challenge. Therefore a minimal probe size is required which can be achieved using a Gas Field Ionization Source (GFIS) in a Helium Ion Microscope (HIM). Due to the high brightness of up to 5•109 A•cm-2•sr-1 and the sharp primary ion energy of 30000 ± 1 eV spot sizes of 0.5 nm can be achieved.
Besides the probe size, the nanoscale analysis is limited by the extremely small amount of sample material and the resulting severe ion beam damage. Only the combination of the techniques with highest degree of information could reveal the composition of nanoscale objects.
Secondary Ion Mass Spectrometry (SIMS), as one of the most powerful techniques for surface analysis directly provides information about elemental, molecular and even isotopic composition. However, quantification in mixed layers cannot be done from pure SIMS measurements without comparison to standards. This drawback is partly compensated by Rutherford Backscattering Spectrometry (RBS) but at a loss of sensitivity. In order to combine this compositional information with the high resolution Secondary Electron (SE) imaging correlative microscopy represents the best way.
Recently, we implemented minimal invasive Time of Flight (TOF) spectrometry into the HIM to enable SIMS as well as RBS [1, 2]. The TOF measurements are triggered by blanking the primary ion beam into an existing Faraday cup and release the beam for short time windows to ensure minimal applied fluencies and obtaining a maximum of information from the region of interest.
In the present contribution we intent to present the technical realization of our approach and show results, drawbacks and derive conclusions for the practical use of this promising technique.
[1] N. Klingner, R. Heller, G. Hlawacek, J. von Borany, J.A. Notte, J. Huang, S. Facsko. Ultramicroscopy 162 (2016), 91-97
[2] R. Heller, N. Klingner, G. Hlawacek. Helium Ion Microscopy, Chapter 12, Springer (2016)
Keywords: HIM SIMS Nano TOF
  • Invited lecture (Conferences)
    23rd International Conference on Ion Beam Analysis IBA-2017, 11.10.2017, Shanghai, China

Publ.-Id: 26186 - Permalink


Interaction between Double Diffusive Convection and Solidification in Ammonium-Chloride Solutions
Anders, S.; Eckert, S.;
This paper presents an experimental investigation of thermally and chemically driven convection with simultaneous crystallisation in a concentrated aqueous ammonium-chloride solution. Measurements were performed in a transparent Hele-Shaw cell (200·100·10mm3) between two massive copper blocks equipped with internal water channels controlling the thermal boundary conditions at the upper and lower horizontal boundaries. The temperatures were regulated by thermostats in a range between -20°C and +40°C giving Rayleigh numbers up to around 0.2·10 9 . A double-wall construction with climatisation was implemented in order to avoid thermal losses through the side walls. Temperatures were monitored by thermocouples calibrated to an accuracy better than 0.05K.
Various flow regimes were studied by choosing different temperature boundary conditions.
The focus was on configurations with negative vertical temperature gradients where thermal convection occurs once a critical temperature difference is exceeded. At sufficient supercooling free crystals nucleate in the upper part of the cell, grow and descend due to their higher density compared to the ambient fluid.
The flow field in the liquid was measured by PIV using fluorescent tracer-particles and laser illumination. PTV with LED-background lighting was used to determine the size-evolution and the trajectories of the free-moving crystals. The application of alternating lighting methods and advanced digital image filtering allows for simultaneous operation of PIV and PTV. This approach enables a quantitative study of the interplay of different convection regimes and the solidification process. For example the relation between drag-coefficient, crystal size and crystal growth was investigated.
As a reference case a stable stratification resulting from parallel cooling of the top and bottom walls was investigated. The following solidification phenomena were observed during the experiments: columnar growth at the walls, nucleation and growth of equiaxed crystals in the bulk, chimney-formation in the mushy layer as well as the remelting of columnar and equiaxed dendrites.
Keywords: equiaxed solidification, double diffusive convection, dual phase velocimetry, PTV, PIV
  • Lecture (Conference)
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
  • Contribution to proceedings
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
    Proceedings of the 6th Decennial International Conference on Solidification Processing, London: BCAST, Brunel University London, 978-1-908549-29-7, 350-353

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Publ.-Id: 26185 - Permalink


Combined experimental and numerical analysis of a bubbly liquid metal flow
Krull, B.; Strumpf, E.; Keplinger, O.; Shevchenko, N.; Fröhlich, J.; Eckert, S.; Gerbeth, G.;
The paper proposes a combined experimental and numerical procedure for the investigation of bubbly liquid-metal flows. It describes the application to a model configuration consisting of a recirculating GaInSn flow driven by an argon bubble chain. The experimental methods involve X-ray measurements to detect the bubbles and UDV measurements to gain velocity information about the liquid metal. The chosen numerical method is an immersed boundary method extended to deformable bubbles. The model configuration includes typical phenomena occurring in industrial applications and allows insight into the physics of bubbly liquid-metal flows. It constitutes an attractive test case for assessing further experimental and numerical methods.
Keywords: Bubbly liquid-metal flows, Xray radiography, UDV, GaInSn

Publ.-Id: 26184 - Permalink


Development of an 18F-radioligand for in vivo monocarboxylate transporter 1 (MCT1) tumor imaging with PET
Sadeghzadeh, M.; Brust, P.; Fischer, S.; Moldovan, R.-P.;
Impressive developments in the areas of imaging technology and imaging tracers have strengthened preclinical imaging studies on the “hallmarks of cancer” to provide fundamentals for translation to the clinic. Until today, many positron emission tomography (PET) based molecular biomarkers have been used with that regard [1]. Particularly, significant effort has been dedicated to the development and validation of PET biomarkers for tumor cell proliferation and metabolism. Monocarboxylate transporter 1 (MCT1) is an integral plasma membrane protein which bidirectionally transports lactate and ketone bodies along a concentration gradient and is highly expressed in non-hypoxic regions of human colon, breast, head and neck, lung and other tumors. Accordingly, MCT1 inhibitors are regarded to be of potential clinical use [2]. Since there is no selective PET tracer available based on this class of compounds the aim of this project is the development an 18F-labelled radioligand for in vivo imaging of MCT1-overexpressing brain tumors.
Keywords: Fluorine-18 radioligand, Positron Emission Tomography (PET) imaging, Monocarboxylate transporter 1 (MCT1), Brain Tumor
  • Poster
    Network Meeting of the Alexander von Humboldt Foundation, 18.-20.10.2017, Bielefeld, Germany

Publ.-Id: 26183 - Permalink


Comparison of robust optimized proton planning strategies for dose escalation in pancreatic cancer
Stefanowicz, S.; Zschaeck, S.; Rehm, M.; Jakobi, A.; Stützer, K.; Troost, E. G. C.;
Purpose or Objective
In patients with locally advanced unresectable pancreatic cancer, neoadjuvant or primary radiochemotherapy (RCT) are alternative treatment options. Today, treatment outcome after RCT is poor, in part due to radiosensitive organs at risk (OARs) limiting the prescribed dose to the target volume. Proton beam techniques enable delivering high radiation doses to the target volume while sparing OARs. In this in-silico feasibility study, we assessed different strategies for dose escalation to 66Gy(RBE) using a simultaneous integrated boost technique and robust multi-field optimized intensity modulated (rMFO-IMPT) pencil beam scanned protons and evaluated their robustness.

Material and Methods
For each of six pancreatic cancer patients, four different rMFO-IMPT plans were optimized on free-breathing treatment planning CTs using the RayStation treatment planning system (V5.99, RaySearch Laboratories AB, Sweden). These planning strategies consisted of equally-weighted beams: (S1) two posterior oblique (PO) beams, (S2) lateral right beam and left PO beam, (S3) two PO beams plus right non-coplanar beam, and (S4) three non-coplanar beams. At least 95% of 66Gy(RBE) in 30 fractions was prescribed to 95% of the boost volume (GTV), and 51Gy(RBE) was prescribed to 95% of the CTV (GTV with margin and elective volume). A dose fall-off range of 10 mm around the GTV was preset, and setup and range uncertainty parameters of 3 mm and of 3.5% for GTV and CTV coverage were chosen, respectively. The OAR dose constraints adhered to local guidelines and QUANTEC. For each patient and planning strategy, conformity and homogeneity index (CI, HI) of target doses as well as doses to GTV, CTV, and OARs were calculated. Together with additional robustness evaluations of the worst-case scenarios (±3 mm, ±3.5%) the best planning strategy for dose escalation was sought for.

Results
All nominal plans reached the prescribed dose to the GTV and CTV (Fig. 1a). The CI of all planning strategies was similar (mean CI: 0.6-0.7) even though S3 and S4 were more homogeneous. In some patients, S1 was associated with excess dose to the kidneys (Fig. 1b). Radiation doses (D2%, V45Gy) to the duodenum exceeded the constraints since that OAR was next to or within the target volume, while for the remaining gastrointestinal organs radiation doses were similar for the different strategies and within preset limits (Fig. 1c, d). Overall, S3 and S4 showed the best dose distribution for all OARs. Robustness evaluation of all plans revealed that in total only 38% of the D95% values (S1: 31%, S2: 31%, S3: 39%, S4: 51%) in the worst-case scenarios fulfilled the dose requirement for the GTV leading to an insufficient robustness. Conversely, more than 90% of the D95% values to the CTV were robust against uncertainties, with S3 being most robust (97%).

Conclusion
Disregarding the inter- and intra-fractional organ motion, dose escalation is possible using robust MFO-IMPT plans with three beams, of which at least one non-conformal.
Keywords: Robust planning

Publ.-Id: 26182 - Permalink


Aliovalent cation substitution in UO2: Electronic and local struc-tures of U1-yLayO2±x solid solutions
Prieur, D.ORC; Martel, L.; Vigier, J.-F.; Scheinost, A. C.; Kvashnina, K. O.; Somers, J.; Martin, P. M.
For nuclear fuel related applications, the oxygen stoichiometry of mixed oxides U1-yMyO2±x is an essential property as it af-fects the fuel properties and may endanger the safe operation of nuclear reactors. A careful review of the open literature indicates that this parameter is difficult to assess properly and that the nature of the defects, i.e. oxygen vacancies or UV, in aliovalent cation – doped UO2 is still subject to controversy. To confirm the formation of UV, we have investigated the room temperature stable U1-yLayO2±x phase using several experimental methods (e.g. XRD, XANES and NMR) confirmed by theo-retical calculations. This paper presents the experimental proof of UV and its effect we identified in both electronic and local structure. We observe that UV is formed in quasi equimolar proportion as LaIII in U1-yLayO2±x (y=0.06; 0.11; 0.22) solid solu-tions. The fluorite structure is maintained despite the cationic substitution but the local structure is affected as variations of the interatomic distances are found. Therefore, we provide here the definitive proof that the substitution of UIV with LaIII is not accommodated by the creation of O vacancies as has often been assumed. The UO2 fluorite structure compensates the incorporation of an aliovalent cation by the formation of UV in quasi equimolar proportions
Keywords: UO2, Lanthanum, XANES, EXAFS, NMS

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Publ.-Id: 26181 - Permalink


Inter-center variability in CT-to-SPR conversion in particle therapy: Survey-based evaluation
Taasti, V.; Bäumer, C.; Dahlgren, C.; Deisher, A.; Ellerbrock, M.; Free, J.; Gora, J.; Kozera, A.; Lomax, T.; de Marzi, L.; Molinelli, S.; Teo, K.; Wohlfahrt, P.; Peetersen, J.; Muren, L.; Hansen, D.; Richter, C.;
Purpose/Objective
To assess the inter-center variability of the conversion between CT number and particle stopping power ratio (SPR), a survey-based evaluation was carried out in the framework of the European Particle Therapy Network (EPTN). The conversion is applied to treatment planning CTs to finally derive the proton range in patients. Currently, CT scan protocols for treatment planning are not standardized in image acquisition and reconstruction parameters. Hence, the CT-to-SPR conversion (Hounsfield look-up table, HLUT), depending on the former parameters, has to be defined by each center individually. Aiming to access the current status of inter-center differences, this investigation is a first step towards better standardization of CT-based SPR derivation.
Material/methods
A questionnaire was sent out to particle therapy centers involved in the EPTN and a few centers in the United States. The questionnaire asked for details on CT scanners, acquisition and reconstruction parameters, the calibration and definition of the HLUT, as well as body-region specific HLUT selection. It was also assessed whether the influence of beam hardening (BH) on the HLUT was investigated and if an experimental validation of the HLUT was performed. Furthermore, different future techniques were rated regarding their potential to improve range prediction accuracy.
Results
Twelve centers completed the survey (10 in Europe, 2 in the US). Scan parameters, especially reconstruction kernel and beam hardening correction, as well as the HLUT generation varied widely between centers. Eight of the twelve centers applied a stoichiometric calibration method, while three defined the HLUT entirely based on tissue substitutes, and one center used a combination of both. All facilities performed a piecewise linear fit to convert CT numbers into SPRs, but the number of line segments used varied from 2 to 11 (Table 1). Nine centers had investigated the influence of BH, and seven of them had evaluated the size dependence of their conversion. All except one center had validated their HLUT experimentally, but the validation schemes varied widely. A few things were though found to be common for most centers: 1) CT scans were most commonly acquired at 120 kVp, 2) all centers individually customized their CT-to-SPR conversion, and 3) dual energy CT was seen as a promising technique to reduce CT-related uncertainties (Figure 1).
Conclusion
In general, a large inter-center variability in implementation of CT scans, image reconstruction and especially in CT-to-SPR conversion was found. The benefit of a future standardization is obvious: It would reduce the time-intensive site-specific efforts as well as variations in treatment quality. Due to the interdependency of multiple parameters, no conclusion can be drawn on the derived SPR accuracy and its inter-center variability. As a next step within the EPTN, an inter-center comparison of CT-based SPR prediction accuracy will be performed with a ground-truth phantom.
Keywords: proton therapy, Stopping power ratio, CT, HLUT
  • Lecture (Conference)
    ESTRO 37, 20.-24.04.2018, Barcelona, España
  • Poster
    57th Annual Meeting of the Particle Therapy Co-Operative Group (PTCOG), 21.-26.05.2018, Cincinnati, USA
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 127(2018), S533-S534
    DOI: 10.1016/S0167-8140(18)31279-9

Publ.-Id: 26180 - Permalink


Spin-wave reciprocity in the presence of Néel walls
Körber, L.ORC; Wagner, K.; Kákay, A.ORC; Schultheiß, H.ORC
The reciprocity of spin-wave propagation in 180° Néel walls and surrounding domains is studied. For this, the dispersion relation, phase fronts and spin-wave intensities are analyzed via micromagnetic simulations. Despite the in-plane curling of the magnetization, the domain wall itself acts as a reciprocal channel, whereas non-reciprocal spin-wave propagation is found within the domains. Since the spin-wave localization depends on the selected frequency, this may allow to control the degree of propagation asymmetry.
Keywords: Nanomagnetics, spin waves, domain wall, reciprocity, micromagnetics

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Publ.-Id: 26179 - Permalink


Laboratory-scale X-ray absorption spectroscopy approach for actinide research: Experiment at the uranium L3-edge
Bes, R.; Ahopelto, T.; Honkanen, A.-P.; Huotari, S.; Leinders, G.; Pakarinen, J.; Kvashnina, K. O.;
We report the first proof of principle of an efficient and cost-effective bentchtop alternatives to synchrotron radiation beamlines to perform at laboratory scale Xray Absorption Spectroscopy (XAS) at the U L3-edge in transmission mode. We find excellent agreement with synchrotron-based studies for concentrated samples, in reasonable acquisition time, for UO2, KUO3 and b-UO3 samples. The approach described here already constitutes an inexpensive answer to the XAS beamline over-subscription in the field of actinide’s research for state of the art experiments.
Moreover, our results opens the door to many future applications in the field of actinide’s research, including f-electron chemistry, environmental chemistry and nuclear energy physico-chemistry such as advanced nuclear fuel and long term
nuclear waste disposal.

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  • Secondary publication expected

Publ.-Id: 26178 - Permalink


New insight in the uranium valence state determination in UyNd1-yO2-x
Bes, R.; Kvashnina, K.; Rossberg, A.; Dotavio, G.; Desgranges, L.; Pontillon, Y.; Solari, P. L.; Butorin, S. M.; Martin, P.;
The charge compensation mechanisms in UyNd1-yO2-x and its consequence on the overall O stoichiometry (or O/M ratio where M=Nd+U) have been studied through the uranium valence state mixture evolution as a function of Nd content up to y=0.62 by means of high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) at the U M4-edge. Our results clearly demonstrate the formation of U5+ at low Nd content (y < 0.15). Upon increasing the Nd content, oxygen vacancies and the formation of U6+ appear as competing mechanisms for intermediate Nd concentrations, leading to the co-existence of U4+/U5+/U6+ mixed valence and an overall hypostoichiometry (O/M < 2.00). Finally, the formation of U6+ associated with strongly distorted U local environment is observed for high Nd concentrations (y=0.62), leading to an overall hyperstoichiometry (O/M < 2.00)

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  • Secondary publication expected

Publ.-Id: 26177 - Permalink


Electronic structure studies of bismuth compounds by high energy resolution X-ray spectroscopy and ab-initio calculations
Mistonov, A. A.; Chumakov, A. P.; Ermakov, R. P.; Iskhakova, L. D.; Zakharova, A. V.; Chumakova, A. V.; Kvashnina, K. O.;
Bismuth-based compounds are widely used as superconductors, catalysts and material for optical devices. Its properties and possibilities to control it are determined by the electronic structure and local environment of Bi-centres. Although x-ray spectroscopy is a powerful method to reveal the crystal and electronic structures, the results obtained so far were limited by the energy resolution of the experimental data. Here we report, for the first time, x-ray absorption near edge structure (XANES) data, recorded in high energy resolution uorescence detection (HERFD) mode at the Bi LIII and LI edges for the number of bismuth compounds. Experimental data are analyzed by ab initio calculations, using finite difference method (FDMNES) code for metallic Bi, Bi2O3, BiPO4, Bi4(GeO4)3 and NaBiO3 compounds. It is shown, that oxidation state as well as Bi-ligand bonds length determines the exact position of the absorption edge. Additionally, the strong Bi p-d orbital mixing is observed. The obtained results can be used as an input for the further electronic structure investigations of the bismuth compounds, in different chemical states.

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  • Secondary publication expected

Publ.-Id: 26176 - Permalink


Investigating spin-transfer torques induced by thermal gradients on magnetic tunnel junctions using microcavity ferromagnetic resonance
Cansever, H.; Fowley, C.; Narkovic, R.; Lenz, K.; Kowalska, E.; Yildirim, O.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Deac, A. M.;
Similar to electrical currents flowing through magnetic multilayers [1], it has been predicted that thermal gradients applied across the spacer of a spin-valve or a magnetic tunnel junction may induce pure spin currents and generate ‘thermal’ spin-transfer torques (T-STTs) large enough to induce magnetization dynamics [2-3]. Nevertheless, providing detailed experimental studies in this direction has so far proved elusive, due to difficulties in generating sufficiently large thermal gradients for such effects to be observed. Here, we describe a different approach, which focuses on observing and quantifying spin-transfer torques induced by thermal gradients in magnetic multilayers by means of ferromagnetic resonance (FMR) response under open circuit conditions. The FMR response is measured using specially designed planar microresonators, which generate ac fields perpendicular to the plane of the layers [4]. Such microresonators, with loop diameters of 10 and 20 μm were optimized at a fixed frequency of 14 GHz. Magnetic multilayers with different compositions were patterned using electron-beam lithography into micron-sized pillars with different cross-sections. Microresonators were fabricated using UV lithography such that the magnetic device lies in the center of the loop. An example is shown in Fig 1. For laser heating, we used a diode laser with 51 mW power (5-10 μm focus in diameter). Fig 2 shows a set of FMR measurements performed on an 8x10 μm elliptical shape Py/Cu/Py magnetic multilayer under laser heating, with different laser powers. A clear change is observed at higher than 30 mW laser power, with the FMR line exhibiting changes in resonance field and linewidth. These changes likely arise from a combination of the induced TSTT and the heating of the whole device. The results are analyzed by means of conventional FMR modeling and the thermal gradients are estimated from COMSOL simulations.This project is funded by DFG Priority Programme SPP 1538 Spincaloritronics (SpinCat) and supported by the Nanofabrication Facilities at Ion Beam Center.
Keywords: thermal spin transfer torque, microresonator, ferromagnetic resonance, magnetic tunnel junction.
  • Lecture (Conference)
    Magnetism and Magnetic Materials MMM 2017, 06.-10.11.2017, Pittsburgh, PA, USA

Publ.-Id: 26175 - Permalink


Decoupling the two roles of Ga droplets in the self-catalyzed growth of GaAs nanowires on SiOx/Si(111) substrates
Tauchnitz, T.ORC; Nurmamytov, T.; Hübner, R.; Engler, M.ORC; Facsko, S.; Schneider, H.; Helm, M.; Dimakis, E.ORC
Liquid Ga droplets play a double role in the self-catalyzed growth of GaAs nanowires on Si(111) substrates covered with a native SiOx layer: they induce the formation of nano-sized holes in SiOx and then drive the uniaxial nanowire growth directly onto the underlying Si. The independent control of the two mechanisms is a prerequisite for mastering the growth of nanowires, but it is challenging in a conventional growth procedure where they both take place under the same droplets. To that end, we have developed an in situ procedure where the Ga droplets used for the formation of SiOx holes are removed before new Ga droplets drive the growth of GaAs nanowires. In that way, it was made possible to study the interaction between Ga droplets and SiOx, to create holes in SiOx with controlled number density and size and, finally, to grow GaAs nanowires only within those holes. Our results show unprecedented control of the nanowire nucleation with unique possibilities: (1) deliberate control of the number density of nanowires within three orders of magnitude (106-109 cm-2) without patterning the substrate and without changing the growth conditions, (2) highly synchronous nucleation events and, thus, exceptionally narrow nanowire length distributions (standard deviation < 1 % for 3 mm long nanowires), (3) high yield of vertical nanowires up to 80 % (against GaAs islands), (4) highly reproducible results, and (5) independent control of the nanowire diameter from the number density. We anticipate that our methodology could be also exploited for different materials or other types of nanostructures.

Publ.-Id: 26174 - Permalink


AER Working Group D on VVER Safety Analysis – Report of the 2017 Meeting
Kliem, S.ORC
The AER Working Group D on VVER reactor safety analysis held its 26th meeting in Erlan-gen, Germany, during the period 10-11 May, 2017. The meeting was hosted by AREVA Germany and was held in conjunction with the 11th workshop on the OECD Benchmark for Uncertainty Analysis in Best-Estimate Modelling (UAM) for Design, Operation and Safety Analysis of LWRs. Altogether 11 participants attended the meeting of the working group D, all 11 from AER member organizations. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.
The meeting started with a general information exchange about the recent activities in the participating organizations.
The given presentations and the discussions can be attributed to the following topics:
• Safety analyses methods and results
• Code development and benchmarking
• Future activities
A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.
  • Contribution to proceedings
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland
    Proceedings of the 27th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest, 9789637351280, 11-18
  • Lecture (Conference)
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland

Publ.-Id: 26173 - Permalink


Production of Amphiphilic Hydroxamate Siderophores Marinobactins by Marinobacter sp. DS40M6 for Bioflotation Process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.;
Marinobacter sp. DS40M6 produces the siderophores marinobactins, which are amphiphilic and contain hydroxamate functional groups responsible for a strong complexation of iron(III). First tests about growth and production conditions showed on the one hand a high rate for both growth of bacteria and siderophore production at 25°C. The pH value, on the other hand, demonstrated a contrary effect, thus the optimal pH 7.0 for growth was not the most efficient pH value for siderophore production.

Publ.-Id: 26172 - Permalink


Bioflotation with amphiphilic siderophores
Schrader, S.; Kutschke, S.; Pollmann, K.; Rudolph, M.;
Siderophores are small organic molecules with a high affinity for binding Fe(III) and the ability to form strong complexes. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment.
The biotechnological production of siderophores offers the application in very different fields. For example, they are used as medicine against iron or heavy metal poisoning. Other applications are their utilization for the extraction, recovery and treating of iron as well as other elements, that also can be bound by siderophores. In addition, their application in froth flotation processes could be an attractive novel approach. Molecules produced by the chemical industry with functional groups like hydroxamates have been already applied successfully in this processing method. It can be suggested that siderophores carrying the same functional groups should also work well as collectors. Particularly the group of amphiphilic siderophores that have both hydrophilic and hydrophobic areas are very interesting. The natural hydrophobic property of these chelating agents could avoid additional chemicals and further working steps for making the target mineral particles hydrophobic for an efficient flotation process.
The main advantage of using biotechnology for the production of siderophores is the wide natural diversity of the structures. A lot of microorganisms and their produced siderophores have already been identified and analyzed in detail. So there is an enormous variety of different molecules available. The aim of this study is to test for the first time, whether it is possible to use siderophores in flotation processes. In addition optimized processes for both the biotechnological production and the froth flotation have to be developed. This presupposes also the investigation and characterization of the binding properties during these procedures.
  • Lecture (Conference)
    Mineral Engineering Conference 2017, 20.-23.09.2017, Wisła, Poland

Publ.-Id: 26171 - Permalink


Bioflotation – Kombination der Biotechnologie mit dem klassischen Prozess der Flotation
Schrader, S.; Kutschke, S.; Pollmann, K.; Rudolph, M.;
Die Idee der Verknüpfung von Biotechnologie mit der Aufbereitung von Mineralien wurde auf den Gebieten Bioleaching von Metallen und Bioremediation mineralischer Abfälle bereits eingehend untersucht. Ein neues Interessensgebiet ist nun die Kombination von Biotechnologie mit dem klassischen Prozess der Flotation.
  • Poster
    Tagung Aufbereitung und Recycling, 08.-09.11.2017, Freiberg, Deutschland

Publ.-Id: 26170 - Permalink


Production of amphiphilic hydroxamate siderophore marinobactin by Marinobacter sp. DS40M6 for bioflotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.;
Siderophores are small biomolecules (400-1500 Da) with the ability to form strong complexes with Fe(III) and other metals. A wide range of siderophore structures are already well-known.
The biotechnological production of these organic compounds with bacteria enables them to be used for extracting and recycling metals.
The application of siderophores in traditional froth flotation process enables the development of a sustained bioflotation.
Keywords: siderophores; marinobactin; bioflotation
  • Poster
    22. International Biohydrometallurgy Symposium 2017, 24.-27.09.2017, Freiberg, Deutschland

Publ.-Id: 26169 - Permalink


Variability in crystal surface reactivity: A critical constraint for reactive transport modeling
Fischer, C.;
Reactive transport modeling of fluid-solid interactions relies on (i) contrasts in fluid flow velocity and (ii) variability of surface reactivity. The first point is based on data from, e.g., PET and µCT techniques. The second point, however, is usually addressed by simple kinetic data only. Thus, it neglects information about the intrinsic variability of crystal surface reactivity that often results in a rate range of 2-3 orders of magnitude (1). Such variability is however an important constraint for the evolution of surface roughness and porosity pattern in crystalline matter (2). Here, we highlight important sources of the intrinsic variability of crystal surface reactivity and their impact on surface reaction rates. Rate maps (3) and rate spectra (4) provide critical information about the spatial and temporal variability of surface reactivity that is required to predict the evolution of porosity pattern in crystalline matter (5).

1. Luttge A, Arvidson RS, & Fischer C (2013) A Stochastic Treatment of Crystal Dissolution Kinetics. Elements 9(3):183-188.
2. Fischer C, Kurganskaya I, Schäfer T, & Luttge A (2014) Variability of Crystal Surface Reactivity: What do we know? (Review Article). Applied Geochemistry 43:132-157.
3. Fischer C & Luttge A (2017) Beyond the conventional understanding of water–rock reactivity. Earth and Planetary Science Letters 457:100-105.
4. Fischer C, Arvidson RS, & Luttge A (2012) How predictable are dissolution rates of crystalline material? Geochimica et Cosmochimica Acta 98:177-185.
5. Michaelis M, Fischer C, Colombi Ciacchi L, & Luttge A (2017) Variability of Zinc Oxide Dissolution Rates. Environmental Science & Technology 51(8):4297-4305.
  • Poster
    Reactive Transport in the Earth and Environmental Sciences in the 21st Century, 02.-05.10.2017, Amboise, Frankreich

Publ.-Id: 26168 - Permalink


Manipulation of antiferromagnetic domain distribution in Mn2Au by ultrahigh magnetic fields and by strain
Sapozhnik, A. A.; Abrudan, R.; Skourski, Y.; Jourdan, M.; Zabel, H.; Kläui, M.; Elmers, H. J.;
Evidence for a spin reorientation in antiferromagnetic (AFM) Mn2Au thin films induced by high magnetic fields as well as by the application of in-plane mechanical stress is provided. The AFM domain population in the samples was investigated by resonant X-ray Magnetic Linear Dichroism (XMLD) measurements at the L3 edge of Mn using a variable linear polarization of the incident photon beam. As grown samples show no XMLD signal due to averaging over a random AFM domain distribution. After the exposure to a 70 T in-plane magnetic field a clear XMLD signal indicating the generation of a preferential AFM domain orientation is obtained. The same type of XMLD signal is observed when the thin films are strained, demonstrating the feasibility of AFM Domain manipulation by magnetic fields and stress in Mn2Au.

Publ.-Id: 26167 - Permalink


Magnetic structure in a U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T
Prokes, K.; Bartkowiak, M.; Rivin, O.; Prokhnenko, O.; Förster, T.; Gerischer, S.; Wahle, R.; Huang, Y.-K.; Mydosh, J. A.;
We report a high-field-induced magnetic phase in a single crystal of U(Ru0.92Rh0.08)2Si2. Our neutron study, combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at μ0H = 21.6 T has an uncompensated commensurate antiferromagnetic structure with a propagation vector Q2 = (2/3 0 0) possessing two single-Q domains. U moments of 1.45(9)μB directed along the c axis are arranged in an up-up-down sequence propagating along the a axis, in agreement with bulk measurements. The U magnetic form factor at high fields is consistent with both the U3+ and U4+ types. The low-field short-range order that emerges from pure URu2Si2 due to Rh doping is initially strengthened by the field but disappears in the field-induced phase. The tetragonal symmetry is preserved across the transition, but the a-axis lattice parameter increases already at low fields. Our results are in agreement with an itinerant electron model with 5f states forming bands pinned in the vicinity of the Fermi surface that is significantly reconstructed by the applied magnetic field.

Publ.-Id: 26166 - Permalink


Magnetic field induced tunneling and relaxation between orthogonal configurations in solids and molecular systems
Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Baryshnikov, K. A.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Korostelin, Y. V.;
We report the effect of magnetic field induced quantum tunneling and relaxation transitions between orthogonal configurations in polyatomic systems where no tunneling is expected. Typical situations of this kind occur in molecular systems and local centers in crystals in ground and excited electronic T states, subject to the T⊗e problem of the Jahn-Teller effect, where the wave functions of the three tetragonally distorted configurations are orthogonal. A detailed microscopic theory of this effect shows how the magnetic field violates the orthogonality between the latter allowing for tunneling and relaxations, which decrease in strong fields due to the induced decoherence. The novel effect is demonstrated experimentally as a big, sharp peak in ultrasound attenuation by Cr2+ centers in ZnSe:Cr2+ in the magnetic field B = 0.15 T at the temperature below 8 K. It may influence a variety of magnetic, electronic, and photonic properties of any system in an electronic T state.

Publ.-Id: 26165 - Permalink


Neutron imaging of froth structure and particle motion
Heitkam, S.; Rudolph, M.; Lappan, T.; Sarma, M.; Eckert, S.; Trtik, P.; Lehmann, E.; Vontobel, P.; Eckert, K.ORC
This article reports on the simultaneous measurement of foam structure and attached particles employing neutron imaging. An aqueous foam sample is placed in the NEUTRA beamline at PSI, enabling a spatial resolution of less than 200 micron to be achieved at a frame rate of more than 1 Hz. A forced drainage setup allows the liquid content of the foam to be controlled. The averaged attenuation of the neutrons is demonstrated to yield the liquid fraction of the foam. Hydrophobized gadolinium particles with a diameter of 200 microns are added to the foam. Using two surfactants, different levels of hydrophobicity are achieved. Depending on the drainage flow and the hydrophobicity, the particles are washed out of the foam at different rates. An avalanche-like motion of particle clusters is observed. Neutron radiography is demonstrated to yield unique insights into the unsteady froth flotation process.
Keywords: Neutron imaging, Flotation, Froth, Particle Tracking

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  • Secondary publication expected

Publ.-Id: 26164 - Permalink


Coarsening evolution of dendritic sidearms: from synchrotron experiments to quantitative modeling
Neumann-Heyme, H.; Shevchenko, N.; Lei, Z.; Eckert, K.ORC; Keplinger, O.; Grenzer, J.; Beckermann, C.; Eckert, S.
The local dynamics of dendritic sidearms during coarsening are studied by combining in-situ radiography observations with numerical and analytical models. A flat sample of a Ga-In alloy is partially solidified and then held isothermally in a vertical temperature gradient. The evolving dendritic microstructure is visualized using synchrotron X-ray imaging at the BM20 (ROBL) beamline at ESRF, France. During the coarsening stage, the temporal evolution of the geometrical features of sidebranches is captured by automated image processing. This data is used to quantify the dynamics of two basic evolution mechanisms for sidebranches: retraction and pinch-off. The universal dynamics of sidearm necks during pinch-off are exploited to determine the product of liquid diffusivity and capillarity length, Dd_0, as a parameter that is crucial in the calibration of quantitative models. By employing an idealized phase-field model for the evolution of a single sidebranch, the behavior of selected sidebranches is reproduced from the experiments in a consistent way.
Keywords: Dendritic solidification; microstructure; coarsening; sidearm detachment; X-ray radiography; phase-field model; material properties

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  • Secondary publication expected

Publ.-Id: 26163 - Permalink


Structural and thermodynamic investigation of AnIVLI(O)HOPO(Article)
Aupiais, J.; Younes, A.; Moisy, P.; Hennig, C.; Rossberg, A.; Brunel, B.; Kerbaa, M.; Vidaud, C.; Den Auwer, C.;
For the first time, capillary electrophoresis coupled with inductively coupled plasma mass spectrometry has been used to determine the stability constants of PuIV with the multidentate hydroxypyridinonate chelating agents 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO) in 0.1 M NaNO3 solution, pcH = 1.395 at 25 °C through competition with the NTA ligand. The limiting electrophoretic mobility was found to be zero for AnIV[5-LIO(Me-3,2-HOPO)] and slightly positive for AnIV[3,4,3-LI(1,2-HOPO)] (AnIV = Th, Pu). They were respectively assigned to the formation of the 1:2 neutral species An[5-LIO(Me-3,2-HOPO)]2 and a mixture of the neutral species AnIV[3,4,3-LI(1,2-HOPO)] and its protonated form AnIVH[3,4,3-LI(1,2-HOPO)]+. The corresponding stability constants of ThIV with both chelators were evaluated through the same experiments for the sake of comparison. The stability of both PuIV-HOPOs was about ten orders of magnitude better than that of the equivalent ThIV complexes. To complement these thermodynamic data, structural parameters of Pu[3,4,3-LI(1,2-HOPO)] and Th[3,4,3-LI(1,2-HOPO)] complexes in solution have been derived from EXAFS experiments and compared to previously reported crystallographic structures.

Publ.-Id: 26162 - Permalink


Calibration of scintillation screens for ultrashort electron bunch detection
Kurz, T.; Couperus, J. P.ORC; Krämer, J. M.; Ding, H.; Kuschel, S.; Köhler, A.; Zarini, O.; Hollatz, D.; Schinkel, D.; D‘Arcy, R.; Schwinkendorf, J. P.; Irman, A.; Schramm, U.; Karsch, S.
This work reports on the calibration of scintillating screens for diagnoses of high-charge density electron beams origination from laser plasma accelerators (LPA). Our setup at the conventional ELBE accelerator is cross-calibrated with an integrating current transformer (ICT) and allows for calibration over a large charge density range, thus enabling the study both the linear and non-linear scintillating screen response, as well as long-term stability tests of the screens. In contrast to previous works, the calibration presented here is performed under conditions with a close mimic to real experimental LPA conditions.
A linear response of the scintillator to the applied electron charge was found, followed by a saturation process starting in the range of nC/mm^2. Mimicking a 1-Hz LPA, long–term stability tests showed a significant decrease of the scintillation efficiency over time.
Finally, we present a method where a LED-based constant light source provides an easy method for absolute calibration of charge diagnostic systems at LPAs. This method eliminates many potential error sources existing in currently used methods and enables the transfer of absolute charge calibrations between laboratories.
  • Poster
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy

Publ.-Id: 26161 - Permalink


Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator
Couperus, J. P.ORC; Pausch, R.; Köhler, A.; Zarini, O.; Krämer, J. M.; Kurz, T.; Garten, M.; Huebl, A.; Gebhardt, R.; Helbig, U.; Bock, S.; Zeil, K.; Debus, A.; Bussmann, M.; Schramm, U.; Irman, A.
Laser-plasma wakefield acceleration is capable of producing quasi-monoenergetic electron beams reaching into the GeV range with few-femtoseconds bunch duration. Scaling the charge to the nanocoulomb range would yield hundreds of kiloamperes peak-current and stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and γ-ray sources, compact FELs and laboratory-size beam-driven plasma accelerators. Laser-plasma accelerators generating such high currents operate in the beam loading regime where the accelerating field is strongly modified by the self-fields of the injected bunch, improving the final beam quality if appropriately controlled. Here we experimentally investigate the effects of beam loading at the theoretically predicted limit by loading unprecedented charges of about 0.5 nC within a mono-energetic peak into the first plasma cavity. As the energy balance is reached, the final energy spread is minimized. We show that the beam quality is maintained up to an estimated peak-current of 50 kA, an order of magnitude larger than in state-of-the-art conventional and laser-plasma accelerators.
  • Lecture (Conference)
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy
  • Lecture (Conference)
    Conference on High Intensity Laser and attosecond science in Israel (CHILI), 11.-13.12.2017, Tel-Aviv, Israel

Publ.-Id: 26160 - Permalink


Research on the chemistry of f-elements at HZDR - A general overview of the division Chemistry of the f-Elements
Ikeda-Ohno, A.ORC
Established in June 2014, the division Chemistry of the f-Elements at the Institute of Resource Ecology (IRE) is conducting research on the fundamental physics/chemistry of f-elements, i.e. actinides and lanthanides. This presentation intends to provide a general overview of the recent research activities in the division, in order to possible research overlapping between HZDR-IRE and CEA-Marcoule for future collaborations.
Keywords: actinides, f-elements, coordination, chemistry
  • Lecture (others)
    Internal colloquium, 05.10.2017, CEA-Marcoule, France

Publ.-Id: 26159 - Permalink


Drone-borne hyperspectral monitoring of acid mine drainage. An example from the Sokolov lignite district.
Jackisch, R.; Lorenz, S.; Zimmermann, R.; Möckel, R.; Gloaguen, R.;
This contributions aims to demonstrate the potential of unmanned aerial systems (UAS) to monitor areas affected by Acid mine drainage (AMD). The investigated area covers a recultivated tailing, which is and part of the Sokolov coalmine district in the Czech Republic. A high abundance of AMD minerals occurs in a confined space of the selected test site, which AMD minerals in high abundances can signal potential environmental predicament. The deposited mine waste material contains pyrite and itsthe consecutive weathering products, mainly iron hydroxides and oxides, which affect the natural pH values of the Earth’s surface. While previous research done in this area relies on satellite and air-borne data, our approach focuses on lightweight drone systems providing ground readiness within hours and, thus,, enabling rapid field campaigns. High spatial image resolutions and and precise target determination are additional advantages of UAS-based mapping. During April to September 2016, in total four field and flight campaigns were conducted. For validation, the waste heap was probed in-situ for pH, X-ray fluorescence (XRF) and, reflectance spectrometry. and sSampling points were surveyed by a differential GNSS global navigation satellite systems. Ground truth was achieved by collecting samples that were characterized for pH, X-ray diffraction and XRF in laboratory conditions. Sampling points were surveyed by a differential GNSS global navigation satellite systems. Hyperspectral data were processed and corrected for atmospheric, topographic and illumination effects. High-resolution point clouds and digital elevation models were built from drone-borne RGB data using Structure-from-Motion. The supervised classification of hyperspectral image (HSI) data suggests the presence of jarosite and goethite -, minerals associated with the acidic environmental conditions (pH range = 2.3 – 2.8 in situ). We identified specific iron absorption bands in the UAS-HS data, and was confirmed with ground-truth spectroscopy. The distribution of in-situ pH data supports the UAS-based mineral classification results. Evaluation of the applied methods highlights the drone surveying as a fast, non-invasive, inexpensive technique for multi-temporal environmental monitoring of the post-mining landscape.
Keywords: Hyperspectral; Remote sensing; unmanned aerial system; Acid mine drainage; Iron minerals; Image classification, Sokolov, post-mining

Publ.-Id: 26158 - Permalink


Ion Beam Induced Surface Modification of ta-C Thin Films
Berova, M.; Sandulov, M.; Tsvetkova, T.; Kitova, S.; Bischoff, L.; Boettger, R.;
Thin film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C), deposited by filtered cathodic vacuum arc, were implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3E14 - 3E15 cm-2 and N+ with the same energy and ion fluence D = 3 E14 cm-2. The Ga+ ion beam induced surface structural modification of the implanted material, displayed by formation of new phase at non-equilibrium condition, which could be accompanied by considerable changes in the optical properties of the ta-C films. The N+ implantation also results in modification of the surface structure. The induced structural modification of the implanted material results in a considerable change of its topography and optical properties. Nanoscale topography and structural properties characterisation of the Ga+ and N+ implanted films were performed using atomic spectroscopy analysis. The observed considerable surface structural properties modification in the case of the higher fluence Ga+ implanted samples results from the relatively high concentration of introduced Ga+ atoms, which is of the order of those for the host element.
Keywords: carbon, ion implantation, atomic force microscopy

Publ.-Id: 26157 - Permalink


Visualization of gas-liquid multiphase pseudo-slug flow using Wire-Mesh Sensor
Kesana, N. R.; Parsi, M.; Vieira, R. E.; Azzopardi, B.; Schleicher, E.; Mclaury, B. S.; Shirazi, S. A.; Hampel, U.;
Intermittent two-phase flows are commonly encountered in the petroleum industry. Much attention has been focused by several researchers on intermittent flows existing at low superficial gas velocities (<10 m/s). There is limited work performed on intermittent structures persisting at higher superficial gas velocities (pseudo-slug flows). In the present experimental study, a conductivity-based Wire-Mesh Sensor (WMS) was used to visualize and characterize pseudo-slug flow. Experiments were performed in a 76.2 mm horizontal pipe with air and water as the working fluids at atmospheric conditions. The superficial gas and liquid velocities ranged from 9 m/s to 35 m/s and 0.45 m/s to 0.76 m/s, respectively. A 16 × 16 WMS was placed 17 m away from the pipe inlet to measure spatio-temporal void-fraction distribution. The WMS data acquisition frequency was set to 10 kHz. From the void-fraction time series data, the periodic pseudo-slug structures were visualized. The visualization suggested that unlike slug flow where the liquid structures fill the pipe cross-section, the pseudo-slugs were extremely aerated structures (high gas-liquid mixing) formed due to the gas penetration into the liquid slug body. This paper also presents the measurements of important hydrodynamic characteristics such as cross-sectional averaged void-fraction time series and mean void fraction. The effect of liquid viscosity on the visualized structures is also presented.
Keywords: Flow visualization Intermittent multiphase flows Pseudo-slug flow Slug flow Wire-mesh sensor

Publ.-Id: 26156 - Permalink


Fission and other fast neutron induced reactions investigated at nELBE
Beyer, R.ORC; Junghans, A. R.; Dietz, M.; Kögler, T.; Schwengner, R.; Urlaß, S.; Wagner, A.
The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 10⁴ n/s/cm². The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron production target delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of Pu-242 has been measured in the range from 0.5 to 10 MeV relative to U-235(n,fis) using two fission ionization chambers. A statistical uncertainty down to 1.1 % and systematic uncertainty of about 2.7 % was reached.
Keywords: nELBE, neutron time-of-flight, transmission, inelastic scattering, fission
  • Poster
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Publ.-Id: 26155 - Permalink


Fission measurements at nELBE
Beyer, R.ORC; Dietz, M.; Junghans, A. R.; Kögler, T.; Schwengner, R.; Urlaß, S.
The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 104 n/s/cm2. The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron productiontarget delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of 242Pu has been measured in the range from 0.5 to 10 MeV relative to 235U(n,f) using two fission ionization chambers. A statistical uncertainty down to 1.1% and systematic uncertainty of about 2.7% was reached.
Keywords: nELBE, neutron time-of-flight, fission
  • Invited lecture (Conferences)
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Publ.-Id: 26154 - Permalink


Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi
Kumar, N.; Shekhar, C.; Klotz, J.; Wosnitza, J.; Felser, C.;
LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

Publ.-Id: 26153 - Permalink


Charge Density Waves in Graphite: Towards the Magnetic Ultraquantum Limit
Arnold, F.; Isidori, A.; Kampert, E.; Yager, B.; Eschrig, M.; Saunders, J.;
Graphite is a model system for the study of three-dimensional electrons and holes in the magnetic quantum limit, in which the charges are confined to the lowest Landau levels.We report magneto-transport measurements in pulsed magnetic fields up to 60 T, which resolve the collapse of two charge density wave states in two, electron and hole, Landau levels at 52.3 and 54.2 T, respectively. We report evidence for a commensurate charge density wave at 47.1 T in the electron Landau level, and discuss the likely nature of the density wave instabilities over the full field range. The theoretical modeling of our results predicts that the ultraquantum limit is entered above 73.5 T. This state is an insulator, and we discuss its correspondence to the “metallic” state reported earlier.We propose that this (interaction-induced) insulating phase supports surface states that carry no charge or spin within the planes, but does, however, support charge transport out of plane.

Publ.-Id: 26152 - Permalink


Magnetic field induced phase transitions and phase diagrams of multiferroic Mn0.95Co0.05WO4 with cycloidal spin structure
Urcelay-Olabarria, I.; Ressouche, E.; Wang, Z.; Skourski, Y.; Ivanov, V. Y.; Popov, Y. F.; Vorobev, G. P.; Balbashov, A. M.; Qureshi, N.; Garcia-Munoz, J. L.; Skumryev, V.; Mukhin, A. A.;
Slightly Co-doped MnWO4 at the lowest 5% Co concentration, for which the multiferroic cycloidal phase becomes a ground state, has been studied in magnetic fields up to 60 T by bulk magnetic and electric polarization measurements along different crystallographic directions. The field induced magnetic transitions up to 12 T and the ways they proceed were tracked also by single-crystal neutron diffraction, and the relevant field induced magnetic structures were identified and refined. The complete magnetoelectric phase diagrams for magnetic fields along distinct directions in relation to the cycloidal spin structure have been constructed for magnetic field values exceeding those necessary to induce a spin-flip transition into the paramagnetic state. Their common feature is the existence of nonpolar sinusoidal phases identified by the disappearance of the electric polarization in a field regime slightly below the spin-flip transition. At lower magnetic fields either continuous or abrupt field induced reorientations of the cycloidal magnetic structures were observed, respectively, for a field direction along the crystallographic b axis or along the easy magnetic axis, and the different character of those transitions has been attributed to specific features in the magnetic anisotropy.

Publ.-Id: 26151 - Permalink


Influence of MOCVD Growth Pressure on Magnetoresistance of Nanostructured La-Ca-Mn-O Films Used for Magnetic Field Sensors
Zurauskiene, N.; Pavilonis, D.; Klimantavicius, J.; Balevicius, S.; Stankevic, V.; Kersulis, S.; Plausinaitiene, V.; Abrutis, A.; Lukose, R.; Skapas, M.; Juskenas, R.; Knasiene, B.; Naujalis, E.; Law, J. M.;
The results of structure and magnetoresistance (MR) of nanostructured La1−xCaxMnyO3 (LCMO) films, grown at different gas pressure (from 3 to 7 Torr) by pulse injection metal–organic chemical vapor deposition (MOCVD) technique, are presented. The MR was investigated in pulsed magnetic fields up to 60 T in the temperature range 1.5–294 K. The results were analyzed from the perspective of using these films for magnetic field sensors operating at low temperatures. It was demonstrated that with the increase of Ar + O2 gas pressure, the surface morphology of the films becomes rougher and grain size increases. Also, the ratio of Mn/(La + Ca) increases with the increase of the pressure. Large MR of the films was observed in a wide temperature range below the ferromagnetic–paramagnetic phase transition. It was shown that at cryogenic temperatures, the films grown at gas pressure of 3 Torr have higher sensitivity in lower magnetic field range (<10 T), while in high magnetic fields (20–60 T), the properties of films grown at higher gas pressure 5–7 Torr are favored. The obtained results allow evaluating the influence of MOCVD growth pressure on MR and sensitivity to the magnetic field of LCMO manganites used for pulsed magnetic field sensors.

Publ.-Id: 26150 - Permalink


Structural and Magnetic Properties of the Trirutile-type 1D-Heisenberg Anti-Ferromagnet CuTa2O6
Golubev, A.; Dinnebier, R. E.; Schulz, A.; Kremer, R. K.; Langbein, H.; Senyshyn, A.; Law, J. M.; Hansen, T. C.; Koo, H.-J.; Whangbo, M.-H.;
We prepared trirutile-type polycrystalline samples of CuTa2O6 by low-temperature decomposition of a Cu−Ta−oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure. GGA+U density functional calculations of the spin-exchange parameters as well as magnetic susceptibility and isothermal magnetization measurements reveal that CuTa2O6 is a new 1D Heisenberg magnet with predominant anti-ferromagnetic nearest-neighbor intrachain spin-exchange interaction of ∼50 K. Interchain exchange is a factor of ∼5 smaller. Heat capacity and low-temperature high-intensity neutron powder diffraction studies could not detect long-range order down to 0.45 K.

Publ.-Id: 26149 - Permalink


Coordination polymer (CP) networks and molecular complexes of tetravalent actinides (Th, U, Np) with aromatic polycarboxylate ligands or polyoxometalate (POM) species
Loiseau, T.ORC; Martin, N. P.; Volkringer, C.; Duval, S.; März, J.; Ikeda-Ohno, A.ORC
Coordination polymers are built up from the association of metallic centers with organic (e.g. O- or N-donor) ligands. In the particular case of actinides (An), precedent studies have reported mainly the synthesis of such solid networks bearing U(VI) or Th(IV), while trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of An, the tetravalent state has been investigated most actively and large polyoxo clusters have been isolated for U or Pu. In contrast, there are very few data concerning Np(IV) compounds. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids, or other organic pollutants (e.g. phthalates).
In the present communication, we firstly present the formation of several series of uranyl-organic frameworks associated to poly-carboxylate linkers, by following the pH variation parameter of the reaction medium, related to the hydrolysis rate. This strategy was then applied to actinides(IV), which are known to exhibit a strong affinity for hydrolysis reaction in order to form inorganic entities with high nuclearities. In a first approach, the control of water content in reaction media containing organic solvent will be investigated in different chemical systems with Th(IV) and U(IV) in the presence of dicarboxylic acids molecules (typically terephthalic acid), and was then extended to Np(IV) for some cases. The structural descriptions of the different coordination polymers will point out the nuclearity variation of the inorganic bricks from mononuclear [AnO9] up to hexanuclear entities [An6O8]. The particular case of the poly-oxo cluster [An38] will be discussed, and its formation will be described with U(IV) and Np(IV) in different solvents. The crystallization of the crystallization of U(IV) and Np(IV) with various aromatic polycarboxylate ligands was then considered in water medium and crystal structures of coordination networks with phtalate and mellitate have been analyzed. The last point deals with the isolation and crystallization of polynuclear clusters of actinides (Th(IV)/U(IV)) embedded within large anionic polytungstate moieties ([SiW9O34], [AsW9O33]). Trinuclear, tetranuclear and hexanuclear motifs bearing actinides(IV) have thus been identified in this system.
Keywords: Actinides, tetravalent, coordination polymers, carboxylates, polyoxo-metalate, metal-organic frameworks
  • Invited lecture (Conferences)
    American Chemical Society Annual Meeting, 22.-28.03.2018, New Orleans, USA

Publ.-Id: 26148 - Permalink


QMOM methods for bubbly flows –potentials for simulation of pumps
Hasse, C.; Salenbauch, S.; Pollack, M.; Oertel, R.; Li, D.; Schlegel, F.; Lucas, D.;
The temporal and spatial development of a particle size distribution, e.g. in a bubbly flow, can be described with the so-called Population Balance Equation. It represents a continuity statement for the number density of particles in a flow. The presentation contains a comparison of two prominent approaches for solving the population balance equation, i.e. the family of Quadrature-based Moment Methods and the Method of Classes.
Keywords: Population Balance Modeling, Quadrature-based Method of Moments, Class Methods, Pumps
  • Lecture (others)
    VDMA AK-Mehrphasenströmung, 26.09.2017, Frankfurt, Deutschland

Publ.-Id: 26147 - Permalink


Negative Longitudinal Magnetoresistance from the Anomalous N = 0 Landau Level in Topological Materials
Assaf, B. A.; Phuphachong, T.; Kampert, E.; Volobuev, P. S.; Mandal, P. S.; Sanchez-Barriga, J.; Rader, O.; Bauer, G.; Springholz, G.; de Vaulchier, L. A.; Guldner, Y.;
Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on Pb1−xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N = 0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N = 0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

Publ.-Id: 26146 - Permalink


Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As
Yuan, Y.; Xu, C.; Hübner, R.; Jakiela, R.; Böttger, R.; Helm, M.; Sawicki, M.; Dietl, T.; Zhou, S.;
Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1−xMnxAs and In1−xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1−xMnxAs compared to Ga1−xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.

Publ.-Id: 26145 - Permalink


ASTEC model development for the severe accident progression in a generic AP1000-LIKE
Albright, L.; Wilhelm, P.; Jevremovic, T.;
Improvements in light water reactor (LWR) technologies in recent decades have led to the development of advanced LWRs, currently under construction, soon to join the international fleet of nuclear power plants (NPPs). Enhanced safety capabilities have been achieved in advanced LWRs through the utilization of passive safety systems and design improvements. The progression of severe accidents in advanced LWRs is not well described in the current open literature. To date severe accident analyses performed on the Westinghouse AP1000 have focused on evaluating the performance of the AP1000 safety systems in the prevention of severe accidents, with little focus on characterizing the progression of core degradation to identify the timing of key events such as core uncovery, relocation of corium to the lower plenum, and lower head failure.

An initial, generic model of an AP1000-LIKE reactor has been developed in the severe accident integral code ASTEC to characterize the progression of severe accidents in the AP1000-LIKE model and identify the representation of important physical phenomena and key events of core degradation progression. To evaluate the progression of severe accidents in the AP1000 an accident scenario without accident management measures (AMM), and a complete loss of primary flow is designed and simulated using the developed ASTEC model. The preliminary code results showed the applicability of the model to simulate severe accident scenarios. Without AMM, it is determined that reactor pressure vessel failure occurs nearly four hours after the start of the transient; after the loss of primary coolant flow, a large amount of hydrogen is produced (~800 kg), and a large mass of molten material forms (~150 tons) and relocates to the lower plenum. Future efforts will focus on developing a full plant model for a generic AP1000 and further characterizing the progression of severe accidents.
Keywords: Severe Accidents, Westinghouse AP1000, ASTEC
  • Lecture (Conference)
    IAEA Technical Meeting on the Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors (I3-TM-54660), 09.-12.10.2017, Vienna, Austria

Publ.-Id: 26144 - Permalink


Molecular and Crystal Structures of Uranyl Nitrate Coordination Polymers with Double-headed 2-Pyrrolidone Derivatives
Kazama, H.; Tsushima, S.; Ikeda, Y.; Takao, K.;
Double-headed 2-pyrrolidone derivatives (DHNRP) were designed and synthesized as bridging ligands for efficient and selective separation of UO22+ from HNO3 solution by precipitation. The building blocks, UO2(NO3)2 and DHNRP, were successfully connected to form an infinite 1D coordination polymer. Solubility of [UO2(NO3)2(DHNRP)]n is no longer correlated to hydrophobicity of the ligand, but is exclusively governed by ligand symmetry and packing efficiency. The newly designed DHNRP family can be used to establish a new spent nuclear fuel reprocessing scheme.

Publ.-Id: 26143 - Permalink


Interaction of NpO2+ with Cl– in NaCaCl-type solutions at ionic strength of 6M: Effect of presence of Ca ion on interaction
Nagasakia, S.; Saito, T.; Tsushima, S.; Goguen, J.; Yang, T.;
The interaction of NpO2+ with Cl– was studied using visible–near-infrared spectroscopy in NaClCaCl2NaClO4, NaClNaClO4, and CaCl2NaClO4 solutions with ionic strength (I) of 6M. The spectra of NpO2+ around 980 nm varied with Cl– concentration in the NaClCaCl2NaClO4 and NaClNaClO4 solutions at [Cl–] ≥ 3.5M, but not in the CaCl2NaClO4 solution. Assuming the 1:1 interaction between NpO2+ and Cl–, the apparent equilibrium constants at I = 6M were evaluated. The presence of Ca2+ was found to destabilize overall interaction between NpO2+ and Cl–. The observations were consistent with the density functional theory calculation.
Keywords: Cl–, Density Functional Theory Calculation, Equilibrium Constants, Ionic Strength, NpO2+, Presence of Ca2+
  • Open Access LogoContribution to proceedings
    37th Annual Conference of the Canadian Nuclear Society and 41st Annual CNS/CNA Student Conference, 04.-07.06.2017, Niagara Falls, Canada
    DOI: 10.1016/j.net.2017.08.010

Publ.-Id: 26142 - Permalink


Geostatistical simulation of compositional data in the presence of several geological domains
Talebi, H.; Tolosana-Delgado, R.; Lo, J.; Mueller, U.;
This paper proposes a methodology for geostatistical simulation of compositional data in presence of several geological domains: After applying statistical analysis and compositionally compliant contact analysis on the data set, geological domains with the same compositional characteristics are merged. Plurigaussian simulation (PGS) is utilized to generate multiple numerical models of the remaining domains, with the aim of assessing the uncertainty in the domain boundaries and improving the geological controls in the characterization of compositional attributes. The resulting conditional realisations of geological domains are used to derive the posterior probabilities of occurrence of the domains over the deposit. The compositional data set is classified by geological domain and for each class realisations are generated across the target grid of the resource. The final mineral resource model is obtained by weighting the simulated mineral compositions associated with the different domains by the probabilities of occurrence of each domain. This approach accounts for the uncertainty in the geology of the ore body and spatial variability of mineral composition.

The approach is illustrated through an application to a nickel-cobalt laterite deposit located in Western Australia. A set of 8818 samples is considered in order to provide the conditioning data. Four rock types (Ferruginous, Smectite, Saprolite, and Ultramafic) are considered to define compositionally homogeneous domains. Three major (Fe, Al, and Mg) and two target (Ni and Co) elements are the variables of interest in this study. Since the data are compositional a filler variable is introduced to achieve closure and to retain the intuitive relation between each component and the mass of its associated element.
  • Lecture (Conference)
    Annual Conference of the International Association for Mathematical Geosciences, 04.-07.09.2017, Fremantle, Perth, Australia

Publ.-Id: 26141 - Permalink


Geochemical Interactions of Plutonium with Opalinus Clay Studied by Spatially Resolved Synchrotron Radiation Techniques
Kaplan, U.; Amayri, S.; Drebert, J.; Rossberg, A.; Grolimund, D.; Reich, T.;
Plutonium plays an important role within nuclear waste materials because of its long half-life and high radiotoxicity. The aim of this study was to investigate with high spatial resolution the reactivity of the more oxidized forms of Pu(V,VI) within Opalinus Clay (OPA) rock, a heterogeneous, natural argillaceous rock considered as a potential repository host. A combination of synchrotron based X-ray microprobe and bulk techniques was used to study the spatial distribution and molecular speciation of Pu within OPA after diffusion and sorption processes. Microscopic chemical images revealed a pronounced impact of geochemical heterogeneities concerning the reactivity of the natural barrier material. Spatially resolved X-ray absorption spectroscopy documented a reduction of the highly soluble Pu(V,VI) to the less mobile Pu(IV) within the argillaceous rock material, while bulk investigations showed second-shell scattering contributions, indicating an inner-sphere sorption of Pu on OPA components. Microdiffraction imaging identified the clay mineral kaolinite to play a key role in the immobilization of the reduced Pu. The findings provide strong evidence that reduction and immobilization do not occur as linked processes on a single reactive phase but as decoupled, subsequent, and spatially separated reactions involving different phases of the OPA.
Keywords: Plutonium opalinus clay sorption XAS ROBL

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Publ.-Id: 26140 - Permalink


Zur Mineralogie von Vulkaniten im Bereich des Kemmlitzer Porphyrs (Oschatz Formation, Nordwestsächsisches Becken)
Götze, J.; Lessig, F.; Möckel, R.; Georgi, U.;
Kurzfassung
Mineralogische und geochemische Untersuchungen an Proben des Kemmlitzer Porphyrs sowie von Lithophysen (Hochtemperatur- Kristallisationsdomänen) im entsprechenden Verbreitungsgebiet wurden durchgeführt, um eine mineralogisch-petrographische Charakteristik dieser vulkanischen Bildungen und deren Zuordnung zu möglichen Muttergesteinen zu ermöglichen. Phasenanalytische Untersuchungen (Röntgendiffraktometrie, Mikroskopie, Kathodolumineszenz - KL) erbrachten eine monotone Mineralzusammensetzung, die von Quarz und den beiden Kalifeldspatphasen Sanidin und Orthoklas dominiert ist. Anhand der geochemischen Charakteristika (RFA) lassen sich die untersuchten Vulkanite als Rhyolithe einstufen. Das Vorkommen von hypidiomorphen Quarzphänokristen, z.T. mit Resorptionserscheinungen, gut erhaltenen Kalifeldspäten sowie das Fehlen von Glas-Shards und Fiamme (Bimsfetzen) deuten darauf hin, dass es sich bei den vulkanischen Ablagerungen im Untersuchungsgebiet um Laven und keine Pyroklastite (Ignimbrite) handelt.
Aus den deutlichen Übereinstimmungen hinsichtlich mineralogischer Zusammensetzung, chemischer Charakteristik und textureller Ausbildung kann geschlussfolgert werden, dass alle untersuchten Proben einem vulkanischen Ereignis (Kemmlitzer Porphyr) zuzuordnen sind. Auftretende Unterschiede sind im Wesentlichen auf sekundäre Alterationen zurückzuführen. Das übereinstimmende Erscheinungsbild der Phänokristen sowie deren KL-Eigenschaften deuten auf eine Herkunft aus einer gemeinsamen Schmelze hin. Obwohl die mineralogischen, geochemischen und texturellen Ähnlichkeiten von Lithophysen und Kemmlitzer Porphyr auffällig sind, konnten bisher im massiven, porphyrisch ausgebildeten Vulkanit keine sphärolithischen Bildungen nachgewiesen werden. Randliche Anhaftungen von Pechsteinrelikten an den Lithophysen verschiedener Vorkommen lassen dagegen vielmehr auf eine Bildung im Bereich einer glasigen Fazies schließen.

Abstract
Mineralogical and geochemical investigations of the Kemmlitz porphyry and lithophysae (high-temperature crystallization domains) in the associated area were carried out to get information concerning mineralogical-petrographical characteristics of these volcanic formations and their relation to possible parent rocks. An integrated analytical study by X-ray diffraction, microscopy and cathodoluminescence (CL) revealed a monotonic mineral composition dominated by quartz, sanidine and orthoclase. The rocks can be classified as rhyolite based on the chemical composition (XRF). The predominance of hypidiomorphic quartz phenocrysts, partially with resorption features, well preserved K-feldspar as well as the lack of glass shards and fiamme indicate that the volcanic rocks derive from lava flows and are not related to ignimbrites.
The investigated samples can probably be related to the same volcanic event (Kemmlitz porphyry) because of the similarities in mineral composition, chemical characteristics and texture. Detected variations mainly result from secondary alteration processes. The consistent appearance of phenocrysts and their CL characteristics indicate the origin from a common melt source. Despite these mineralogical, chemical and textural similarities between the Kemmlitz porphyry and the lithophysae, no spherulithic aggregates have been found within the massive porphyric volcanics. Marginal relics of pitchstone on some of the lithophysae instead indicate their formation in a glassy facies.
Keywords: Porphyr, Mineralogie, Nordwestsachsen
  • Contribution to external collection
    in: Veröffentlichungen des Museums für Naturkunde Chemnitz, Chemnitz: Museum für Naturkunde, 2017, 133-150

Publ.-Id: 26139 - Permalink


Measurements of neutron scattering angular distributions with a new scintillator setup
Pirovano, E.; Beyer, R.; Junghans, A. R.; Nolte, R.; Nyman, M.; Plompen, A.;
A new experimental setup for the measurement of neutron scattering cross sections and angular distributions is currently being developed at the neutron time-of-flight facility GELINA, at the JRC-Geel. Up to 32 liquid organic scintillators are employed for the detection of neutrons scattered from a sample of the investigated material. The differential cross section is measured at eight different angles, and the angleintegrated cross section is obtained from the differential data by numerical integration. Two experiments for the study of scattering on iron were carried out, one at GELINA and the other at nELBE (HZDR). The first results for the angular distributions of elastic scattering in the neutron energy range from 2 to 6MeV are here presented and compared with evaluations from the major nuclear data libraries.
Keywords: nELBE, GELINA, neutron, angular distribution
Related publications
Cross section and neutron angular distribution … (Id 28211) has used this publication of HZDR-primary research data

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Publ.-Id: 26138 - Permalink


Measuring at relevant concentrations – radiolabeling as a versatile tool in nanosafety research
Schymura, S.; Hildebrand, H.; Franke, K.;
The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories, a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabeling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [139Ce]CeO2, [7Be]MWCNT, [7Be]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.
  • Poster
    Scientific Stakeholder Meeting on Nanomaterials in the Environment, 10.-11.10.2017, Dessau, Deutschland
  • Invited lecture (Conferences)
    Scientific Stakeholder Meeting on Nanomaterials in the Environment, 10.-11.10.2017, Dessau, Deutschland

Publ.-Id: 26137 - Permalink


NANOSUPPE - Behavior of engineered nanoparticles in the pathway wastewater - sewage sludge - plant using the examples TiO2, CeO2, MWCNT and quantum dots
Schymura, S.; Fricke, T.; Hildebrand, H.; Neugebauer, M.; Franke, K.;
The Project NanoSuppe is concerned with the behavior of nanoparticles along the pathway wastewater – sewage sludge – plant as this is one of the main expected paths in the life cycle of manufactured nanomaterials (MNMs) and marks the possible preliminary end of life of a MNM when it is removed from contaminated wastewater, as well as the potential reintroduction into the human food chain by the use of contaminated sewage sludge as fertilizer. Hence, work was conducted concerning the fate of MNMs in wastewater treatment plants by means of model WWTPs in the lab. Furthermore, environmental mobility studies concerning colloidal stability of MNMs in natural waters and their interaction with soil and sewage sludge were conducted by means of batch and column experiments. As a last step the uptake of MNMs by plants was investigated from hydroponic media as well as soil/sewage sludge matrices.
As a rather unique feature the used MNMs (TiO2, CeO2, MWCNTs and quantum dots) were radiolabeled to enable their sensitive detection at environmentally relevant concentrations in the complex matrices involved.
  • Invited lecture (Conferences)
    Scientific Steakholder Meeting, 10.-11.10.2017, Dessau, Deutschland
  • Invited lecture (Conferences)
    Scientific Steakholder Meeting, 10.-11.10.2017, Dessau, Deutschland

Publ.-Id: 26136 - Permalink


Studies towards the development of a PET radiotracer for imaging of the P2Y1 receptors in the brain: synthesis, 18F-labeling and preliminary biological evaluation
Moldovan, R.-P.; Wenzel, B.; Teodoro, R.; Neumann, W.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Hey-Hawkins, E.; Krügel, U.; Brust, P.;
Purine nucleotides such as ATP and ADP are important extracellular signaling molecules in almost all tissues activating various subtypes of purinoreceptors. In the brain, the P2Y1 receptor (P2Y1R) subtype mediates trophic functions like differentiation and proliferation, and modulates fast synaptic transmission, both suggested to be affected in diseases of the central nervous system. Research on P2Y1R is limited because suitable brain-penetrating P2Y1R-selective tracers are not yet available. Here, we describe the first efforts to develop an 18F-labeled PET tracer based on the structure of the highly affine and selective, non-nucleotidic P2Y1R allosteric modulator 1-(2-[2-(tert-butyl)phenoxy]pyridin-3-yl)-3-[4-(trifluoromethoxy)phenyl]urea (7). A small series of fluorinated compounds was developed by systematic modification of the p-(trifluoromethoxy)phenyl, the urea and the 2-pyridyl subunits of the lead compound 7. Additionally, the p-(trifluoromethoxy)phenyl subunit was substituted by carborane, a boron-rich cluster with potential applicability in boron neutron capture therapy (BNCT). By functional assays, the new fluorinated derivative 1-{2-[2-(tert-butyl)phenoxy]pyridin-3-yl}-3-[4-(2-fluoroethyl)phenyl]urea (18) was identified with a high P2Y1R antagonistic potency (IC50 = 10 nM). Compound [18F]18 was radiosynthesized by using tetra-n-butyl ammonium [18F]fluoride with high radiochemical purity, radiochemical yield and molar activities. Investigation of brain homogenates using hydrophilic interaction chromatography (HILIC) revealed [18F]fluoride as major radiometabolite. Although [18F]18 showed fast in vivo metabolization, the high potency and unique allosteric binding mode makes this class of compounds interesting for further optimizations and investigation of the theranostic potential as PET tracer and BNCT agent.
Keywords: Purine P2Y1 receptors Positron emission tomography Brain PET tracers Radiometabolites Micellar chromatography Hydrophilic interaction chromatography

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  • Secondary publication expected from 01.03.2020

Publ.-Id: 26135 - Permalink


P1513 - Procedure and apparatus for measuring a d.c. magnetic field based on magnetostrictive effect in magnetic wires
Bali, R.; Kolesar, V.; Vazquez, M.;
The present invention relates to a procedure for measuring a d.c. magnetic field by means of a cylindrical device formed by a magnetostrictive core. A d.c. magnetic field is applied and the mechanical deformation on the device caused by the magnetic field is measured and compared with the obtained measurements from previous calibrations to estimate magnetic field intensity values. The invention also relates to an apparatus for measuring a d.c. magnetic field by means of the indicated procedure. The apparatus comprises:
- a cylindrical sensor element and an abutment/fixing element, such that the cylindrical sensor element experiences mechanical deformation when exposed to the d.c. magnetic field,
- a deformation sensing device configured for detecting the mechanical deformation of the cylindrical sensor element, and
- a processing unit configured for determining the intensity of the d.c. magnetic field based on the detected mechanical deformation of the cylindrical sensor element.
  • Patent
    EP3171189 - Offentlegung: 24.05.2017

Publ.-Id: 26134 - Permalink


Radiolabeling - an appropriate tool to study the environmental fate of engineered nanoparticles
Franke, K.; Schymura, S.; Hildebrand, H.;
To study the environmental fate of nanoparticles it requires versatile tools for detection of nano-particulate materials in complex systems such as soil, sewage sludge or organisms within a wide range of concentration. Challenging are the environmentally relevant low concentrations of nanoparticles and the presence of background concentrations of the respective elements. The radiolabeling of nanoparticles offers an excellent and robust method to enable nanoparticle detection in these complex media down to the ng/L range. Even online in-situ tracing and visualization techniques are accessible to obtain spatio - temporal process information.

Depending on the nature of the nanoparticle and the process of interest different methods for the radiolabeling of nanoparticles can be applied, like the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles.

For our recent studies we produced [44Ti]TiO2, [45Ti]TiO2, [48V]TiO2, [64Cu]CuS, [64Cu]SiO2, [65Zn]CdSe/ZnS, [105Ag]Ag, [110mAg]Ag, [124I]CNTs, [125I]CNTs, [131I]CNTs, [7Be]MWCNT, [139Ce]CeO2 and [194Au]Pt nanoparticles. Due to the choice of the used radionuclide (half-life, decay-mode) and the activity concentrations it was possible to enable different detection methods and time scales for the investigations. All these methods go along with a careful characterization of the radiolabeled nanoparticles in respect of the radiolabeling stability and nanoparticle properties.

The radiolabeled nanoparticles have been successfully used in comprehensive environmental studies, like release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.
  • Invited lecture (Conferences)
    NanoSafety 2017, 11.-13.10.2017, Saarbrücken, Deutschland

Publ.-Id: 26133 - Permalink


P1601 - Verfahren und Vorrichtung
Hoffmann, A.; Speck, O.;
Gemäß verschiedenen Ausführungsformen kann ein Verfahren (100) Folgendes aufweisen: Erzeugen (101) eines Magnetfeldes in einem Bestrahlungsbereich; Bestrahlen (103) des Bestrahlungsbereichs mittels eines Partikelstrahls, welcher spinpolarisierte Partikel aufweist; Erfassen (105) einer Anregung der spinpolarisierten Partikel, welche durch das Magnetfeld bewirkt wird; und Ermitteln (107) einer räumlichen Charakteristik des Partikelstrahls auf Grundlage der Anregung.
  • Patent
    DE102016100638 - Offenlegung: 20.07.2017, Nachanmeldungen: WO

Publ.-Id: 26132 - Permalink


P1602 - Tomographievorrichtung
Barthel, F.; Hampel, U.; Bieberle, A.;
Die Erfindung betrifft eine Tomographievorrichtung mit Mitteln zum Erzeugen eines Elektronenstrahls; einer Ablenkvorrichtung zum Ablenken des Elektronenstrahls; einem Target; einer Steuervorrichtung zur Steuerung der Ablenkvorrichtung mittels Steuerungsdaten derart, dass der Elektronenstrahl an einem Auftreffpunkt auf das Target auftrifft und der Auftreffpunkt entlang mehrerer, in unterschiedlichen Ebenen verlaufender Bahnen geführt wird, wobei an dem Auftreffpunkt Röntgenstrahlung entsteht; und mehreren Röntgendetektoren zum Erfassen der Röntgenstrahlung, wobei jeder der Röntgendetektoren ein sich über alle Ebenen hinweg erstreckendes Detektorelement mit Szintillatormaterial und einen Lichtdetektor zum Erfassen von Szintillationslicht und Erzeugen eines Detektorsignals aufweist; wobei jedes der Detektorsignale basierend auf den Steuerungsdaten derjenigen Ebene zugeordnet wird, in der sich der Auftreffpunkt des Elektronenstrahls auf dem Target während der Erzeugung des Detektorsignals befindet.
  • Patent
    DE102016101787 - Offenlegung 03.08.2017, Nachanmeldungen: WO

Publ.-Id: 26131 - Permalink


P1609 - THz-Antenne und Vorrichtung zum Senden und/oder Empfangen von THz-Strahlung
Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.;
Die Erfindung betrifft eine THz-Antenne und Vorrichtung zum Senden und/oder Empfangen von THz-Strahlung, wobei die THz-Antenne mehrere streifenförmige Elektroden und mehrere streifenförmige Gegenelektroden aufweist, die unter Ausbildung einer periodischen Elektrodenanordnung abwechselnd und parallel zueinander angeordnet sind, wobei jeweils eine Elektrode und eine Gegenelektrode ein Elektrodenpaar definieren, wobei die Elektrode und die Gegenelektrode jedes der Elektrodenpaare mittels photoleitfähigen Materials miteinander verbunden sind, und wobei die Elektroden und die Gegenelektroden mit einer konstanten Breite derart ausgebildet sind, dass die Elektroden eine größere Breite aufweisen als die Gegenelektroden.
  • Patent
    DE102016116900 - Erteilung: 02.08.2017, Nachanmeldungen: WO

Publ.-Id: 26130 - Permalink


Two Point Correlation Measurements in Liquid Metal Duct Flows using Ultrasound Phased Arrays
Mäder, K.; Räbiger, D.; Nauber, R.; Büttner, L.; Eckert, S.; Czarske, J.;
A key to improvements of industrial processes involving liquid metals like continuous steel casting is a good knowledge of the interaction between time-varying magnetic fields and conductive fluids. For investigations in this area, model experiments using low-melting liquid metals are conducted, which require suitable instrumentation for opaque media. Ultrasound Doppler velocimetry allows to measure the flow structures and thus to obtain turbulence statistics. For MHD experiments investigating small-scale and turbulent flows, a spatial resolution in the low millimeter range is required.
However, state of the art systems using arrays of unfocused single transducers are limited in their resolution by the divergence of the far field ultrasound beam. In addition, thus systems allow only one dimensional measurements along the propagation direction of the ultrasound beam. Thus interesting quantities in some experiments like turbulence statistics in the axial direction in duct flows can not be measured.
Using our novel phased array ultrasound Doppler velocimeter (PAUDV), the duct flow of an opaque liquid under the influence of an magnetic field can be studied. The measurement system combines the ultrasound Doppler velocimetry with the phased array technique, which allows to adaptively shape the sound field. Using its possibility to drive phased arrays with up to 256 individual channels simultaneously, the ultrasound beam is dynamically focussed in the measurement area, which increases the spatial resolution. In addition, the cross beam technique is used to enable two component measurements using a single acoustical access. This allows to measure turbulence statistics in the main flow direction of a fluid duct with only one ultrasound array on the duct wall.
Keywords: Ultrasound Phased arrays, flow measurements, liquid metals, duct flows
  • Lecture (Conference)
    16th European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden

Publ.-Id: 26128 - Permalink


Controlled ion beam hyperdoping of silicon nanowires
Berencén, Y.; Prucnal, S.; Wang, M.; Hübner, R.; Böttger, R.; Glaser, M.; Schönherr, T.; Möller, W.; Georgiev, Y. M.; Rebohle, L.; Erbe, A.; Lugstein, A.; Zhou, S.; Helm, M.; Skorupa, W.;
The hyperdoping of semiconductors consists of introducing dopant concentrations far above the equilibrium solubility limits. This results in a broadening of dopant energy levels into an impurity or intermediate band. We have recently demonstrated that hyperdoping bulk Si with Se shows promise for Si-based short-wavelength infrared photodetectors [1]. Lately, silicon nanowires (NWs) have gained increasing importance as building blocks for nanodevices like field-effect transistors, light emitting devices and photovoltaic cells [2, 3]. Therefore, the comparison between hyperdoping Si nanowires and bulk Si is a common issue to be examined, which comes along with the transition from a bulk material to semiconductor NWs.
In this work, we report on non-equilibrium processing for controlled hyperdoping of Si/SiO2 core/shell nanowires previously synthesized by the vapor-liquid-solid method. Our approach is based on Se implantation of the upper half of NWs followed by millisecond flash lamp annealing, which allows for a bottom-up template-assisted recrystallization of the amorphized parts of the NWs via explosive solid-phase epitaxy. The Se-hyperdoped Si NWs are successfully recrystallized and accommodate Se concentrations as high as 1021 cm-3. As a proof of device concept, a single Se-hyperdoped NW-based IR photoconductor is shown. In this way, the combination of ion implantation and flash lamp annealing as a promising nanoscale hyperdoping technology is successfully established.
[1] Y. Berencén, S. Prucnal, Fang Liu, I. Skorupa, R. Hübner, L. Rebohle, S. Zhou, H. Schneider, M. Helm, and W. Skorupa, “Room-temperature short-wavelength infrared Si photodetector,” Sci. Rep. 7, 43688 (2017).
[2] B. Tian, T. Cohen-Karni, Q. Qing, X. Duan, P. Xie and C.M. Lieber, “Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes,” Science 329, 831 (2010).
[3] T. J. Kempa, B. Tian, D.R. Kim, J. Hu, X. Zheng and C.M. Lieber, “Single and tandem axial p-i-n nanowire photovoltaic devices,” Nano Lett. 8, 3456 (2008).
Keywords: Hyperdoping, Si nanowires, ion implantation, flash lamp annealing, impurity band, sub bandgap photoresponse
  • Lecture (Conference)
    E-MRS 2017 Fall Meeting (European-Materials Research Society), Symposium S: Materials- nanoelectronics & nanophotonics, 18.09.2017, Warsaw, Poland

Publ.-Id: 26127 - Permalink


Development of highly potent phosphodiesterase 2A (PDE2A) inhibitors: Synthesis and in vitro evaluation of novel fluorinated tricyclic compounds
Ritawidya, R.; Scheunemann, M.; Brust, P.;
Phosphodiesterases (PDEs) play an important role in degrading the cyclic nucleotide second messengers, cAMP and cGMP. They are involved in many biological processes such as neurological, immune or inflammatory disorders, cancer, and heart diseases [1]. One of the PDEs, PDE2A, is found highly expressed in distinct areas of the brain but also in certain types of cancer [1]. Our goal was to synthesize novel fluorinated tricyclic compounds (FT) derivatives which could potentially be used as radioligands for PDE2A imaging of above-mentioned diseases via Positron Emission Tomography (PET). A key intermediate (compound 5 in the respective poster) was prepared in 4 steps, starting from aniline. Afterwards, two-step Suzuki coupling reaction, as well as bromination [2,3] were employed to introduce different moieties in C-1 and C-8 position of 5 to afford three FT derivatives, so-called FT1, FT2, and FT3. They were successfully prepared in 6-8 % overall yield (7-10 steps). The inhibitory potential of these FT derivatives towards PDE2A3 and other subtypes of PDEs was estimated. The affinity and selectivity of FT1 (82.9 % inhibition of PDE2A3 at 10 nM) was much higher than that of FT2 and FT3 (8.52 % and 13.2 % inhibition, respectively). The IC50 value of FT1 was 3.33 nM. It shows selectivity against PDE1A3, 3A, 4A1, 5A1, 6AB, 7A, 8A1, 9A1, 10A1, and 11A1. It is suggested that FT1 if radiolabeled with the PET radionuclide 18F could be a promising PDE2A imaging agent. Further studies to determine the suitability of FT1 as PET candidate are still needed.
Keywords: PDE2A, Benzoimidazotriazine, PET tracer
  • Poster
    Biotechnology Symposium, 05.10.2017, Leipzig, Deutschland

Publ.-Id: 26126 - Permalink


Dynamo action generated by a precession driven flow in a cylindrical container
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.;
Since many years precession is regarded as an alternative flow driving mechanism that may account, e.g., for remarkable features of the ancient lunar magnetic field or as a complementary power source for the geodynamo. Precessional forcing is also of great interest from the experimental point of view because it represents a natural forcing mechanism that allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a dynamo experiment is under development at Helmholtz-Zentrum Dresden-Rossendorf in which a precession driven flow of liquid sodium with a magnetic Reynolds number of up to Rm=700 will be used to drive dynamo action.

Our present study addresses preparative numerical simulations and flow measurements at a small model experiment running with water. In dependence of precession ratio and Reynolds number the resulting hydrodynamic flow patterns and amplitudes provide the essential ingredients for kinematic dynamo models that are used to estimate whether the particular flow is able to drive a dynamo. In the strongly non-linear regime the flow essentially consists of standing inertial waves. Most remarkable feature is the resonant-like occurrence of a stationary axisymmetric mode which emerges around a precession ratio Ωp/Ωc = 0.1. Kinematic dynamo models applying the time-averaged flow field from the hydrodynamic simulations exhibit dynamo action at a critical magnetic Reynolds number of Rmc=430 which is well within the range that will be achieved in the planned large scale sodium experiment.
Keywords: Dynamo, DRESDYN
  • Poster
    Dynamos and planetary flows today (PHR2017), 16.-17.11.2017, London, Great Britain

Publ.-Id: 26124 - Permalink


Engineering and modifying two-dimensional materials by electron beams
Zhao, X.; Kotakoski, J.; Meyer, J. C.; Sutter, E.; Sutter, P.; Krasheninnikov, A. V.ORC; Kaiser, U.; Zhou, W.
Electron-beam (e-beam) irradiation damage is often regarded as a severe limitation to atomic-scale study of two-dimensional (2D) materials using electron microscopy techniques. However, energy transferred from the e-beam can also provide a way to modify 2D materials via defect engineering when the interaction of the beam with the sample is precisely controlled. In this article, we discuss the atomic geometry, formation mechanism, and properties of several types of structural defects, ranging from zero-dimensional point defects to extended domains, induced by an e-beam in a few representative 2D materials, including graphene, hexagonal boron nitride, transition-metal dichalcogenides, and phosphorene. We show that atomic as well as line defects and even novel nanostructures can be created and manipulated in 2D materials by an e-beam in a controllable manner. Phase transitions can also be induced. The e-beam in a (scanning) transmission electron microscope not only resolves the intrinsic atomic structure of materials with defects, but also provides new opportunities to modify the structure with subnanometer precision.
Keywords: TEM, graphene

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Publ.-Id: 26123 - Permalink


Towards diluted magnetism in TaAs
Liu, Yu; Li, Z.; Guo, L.; Chen, X.; Yuan, Y.; Xu, C.; Hübner, R.; Akhmadaliev, S.; Krasheninnikov, A. V.; N'Diaye, A. T.; Arenholz, E.; Helm, M.; Zhou, S.ORC
Magnetism in Weyl semimetals is desired to investigate the interaction between the magnetic moments and Weyl fermions, e.g., to explore anomalous quantum Hall phenomena. Here we demonstrate that proton irradiation is an effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The intrinsic magnetism is observed with a transition temperature above room temperature. The magnetic moments from d states are found to be localized around Ta atoms. Further, the first-principles calculations indicate that the d states localized on the nearest-neighbor Ta atoms of As vacancy sites are responsible for the observed magnetic moments and the long-ranged magnetic order. The results show the feasibility of inducing ferromagnetism in Weyl semimetals so that they may facilitate the applications of this material in spintronics.

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Publ.-Id: 26122 - Permalink


Substitutional carbon doping of free-standing and Ru-supported BN sheets: A first-principles study
Berseneva, N.; Komsa, H.-P.; Vierimaa, V.; Björkman, T.; Fan, Z.; Harju, A.; Todorovic, M.; Krasheninnikov, A. V.ORC; Nieminen, R. M.
The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of con gurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free- standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.
Keywords: graphene, doping, first-principles calculations

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Publ.-Id: 26121 - Permalink


Ionization and reflux dependence of magnetic instability generation and probing inside laser-irradiated solid thin foils
Huang, L. G.; Schlenvoigt, H.-P.; Takabe, H.; Cowan, T. E.;
When an intense laser accelerated electron beam, with large current density on the order of 10^12 A/cm^2, enters a solid density plasma, it is well-known to be subject to a number of different types of instabilities that cause it to filament. In this work, we investigate the transport instability of a fast electron beam that is imprinted on the self-generated magnetic filaments inside the solid density plasmas using particle-in-cell simulations. By varying collisional ionization models, our simulations show that the atomic ionization process is crucial to determine the structure of the magnetic filaments. We further attribute the generation of bulk magnetic filaments to Weibel-like instability mechanism caused by counter-propagating hot forward-bulk return current streams and counterpropagating hot forward-reflux current streams. It is found that the magnetic fields in the filament channels near the rear surface are around one order of magnitude higher than those near the front surface of the thin solid target. This asymmetry is likely induced by the very different properties of bulk electron stream and hot reflux electron stream in terms of density and velocity distribution. Finally, we propose to probe the magnetic fields inside the solid density plasmas by X-Ray polarimetry via Faraday rotation using X-Ray free electron lasers (XFELs). The synthetic simulations show that XFELs are capable to detect the magnetic fields from relativistic laser-solid interactions.
Keywords: Laser plasma interactions, Weibel instability,XFEL,Faraday rotation

Publ.-Id: 26120 - Permalink


Reactive transport modelling based on actual parameters obtained from GeoPET analysis of column experiments
Karimzadeh, L.; Schymura, S.; Kulenkampff, J.; Franke, K.; Eichelbaum, S.; Lippmann-Pipke, J.; Fischer, C.;
Abstract

GeoPET is the application of positron emission tomography (PET) for direct, non-destructive, quantitative spatiotemporal measurement and visualization of fluid transport in natural geological media on drill-core scale [1-5]. Here, we present new results that focus on reactive transport simulations on a drill core sample in 4D (3D+t) by using velocity fields (vx, vy, vz) obtained from GeoPET measurements of a fractured rock sample.
A mechanically induced fracture was obtained during a geomechanical shear test in a calciferous sandstone drill core sampled from the Permian Kupferschiefer ore formation (Rudna mine, Poland). Column leaching experiments using the core sample (D = 6 cm, L = 10 cm) were carried out in a plexiglas reaction cell in the laboratory at atmospheric pressure. The leaching solutions were injected with constant flow rate of 1 mL/h in three stages: First, a moderately hard synthetic fresh water (pH = 8.5) was used as inflow solution for 22 days in order to remove the salts minerals. Second, an acidic solution with pH of 1.5 (H2SO4) was injected to reduce the carbonat content within another 23 days. In stage three, 0.17 mol/L concentrated ferric iron was added to the acidic inflow solution (pH 1.5, H2SO4) for 20 days in order to dissolve mainly the Cu-sulfid minerals and increase the copper recovery from sample. The tracer transport in the sample was monitored by PET technique and the velocity fields derived by using an image analysing algorithm. The velocity fields then imported in the COMSOL Multyphisics to simulate and calibrate the fluidflow. Three dimensional modeling by means of iCP 1.3[6] (an interface coupling of the finite element based code COMSOL Multiphysics® with the geochemical code PhreeqC[7]) was performed to predict the leaching process and solute transport through the core sample by using kinetic mineral dissolution and precipitation data (BRGM database). The reactive transport model results are compared and refined by using the laboratory column leaching experiments.
Keywords: Reactive transport modeling, GeoPET, Column leaching experiment
  • Poster
    Reactive Transport in the Earth and Environmental Sciences in the 21st Century, 02.-06.10.2017, Amboise, France

Publ.-Id: 26119 - Permalink


Scaling EUV and X-ray Thomson sources to optical free-electron laser operation with Traveling-Wave Thomson-Scattering
Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.;
Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

With TWTS the realization of optical free-electron lasers (OFELs) as well as incoherent radiation sources with orders of magnitude higher photon yields than classic head-on Thomson sources becomes possible with state-of-the-art technology in electron accelerators and laser systems.

The talk will show how pulse-front tilted, petawatt class laser pulses and relativistic electrons work together in a side-scattering geometry, where laser end electron propagation direction of motion enclose an angle, to realize long but compact optical undulators with centimeter to meter-scale interaction distances at sub-millimeter undulator periods. Example setups of TWTS OFELs emitting ultraviolet radiation are presented which are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron bunches can be exploited to compensate for their one percent level energy spreads. Further an experimental setup is presented to generate the tilted TWTS laser pulses. This setup strategy provides dispersion compensation, required due to angular dispersion of the laser pulse, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.
Keywords: Optical free-electron laser, traveling wave, thomson scattering, vuv, euv, x-ray, laser dispersion control
  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2017, Prague, Czech Republic

Publ.-Id: 26118 - Permalink


Design of optical setups for high-yield optical undulators in the Traveling-Wave Thomson-Scattering geometry
Steiniger, K.; Debus, A.; Albach, D.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.;
Traveling-Wave Thomson-Scattering (TWTS) can realize ultra-compact, inherently synchronized and highly brilliant light sources from the ultraviolet to the hard X-ray range. In TWTS ultrashort laser pulses and relativistic electron bunches are utilized in a side-scattering geometry where laser pulse and electron bunch direction of motion enclose an interaction angle. Thereby the laser electric field provides the undulator field in which electrons oscillate and emit radiation during interaction. By employing tilted laser pulses TWTS ensures continuous overlap of laser and electrons while these traverse the laser cross-sectional area. Tilting the laser pulse-front compensates the spatial separation of electrons and laser at begin and end of the interaction originating from their different propagation directions. Combining laser pulse-front tilt and side-scattering in TWTS enables interaction over hundreds to thousands of optical undulator periods, enough to allow for optical free-electron laser (OFEL) operation since microbunching of the electron bunch and thus coherent radiation amplification can be achieved.
After shortly introducing the TWTS scattering geometry, the design of optical setups to generate the tilted TWTS laser pulses is presented in the talk. This setup strategy provides dispersion compensation, required due to angular dispersion of the laser pulse, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups. Determining parameters of the setup is illustrated in an example of an ultraviolet TWTS OFEL and an outlook is given on the design of hard X-ray TWTS sources.
Keywords: Traveling wave, thomson scattering, laser dispersion control, x-ray source
  • Lecture (Conference)
    DPG Frühjahrstagung Dresden, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 26116 - Permalink


IAEA CRP benchmark of ROCOM PTS test case for the use of CFD in reactor design using ANSYS CFX
Höhne, T.;
Over the last 15 years, considerable effort has been expended in assembling the available information on the use of CFD in the nuclear reactor safety field. Typical application areas here are heterogeneous mixing and heat transfer in complex geometries, buoyancy-induced natural and mixed convection, etc., with specific reference to NRS accident scenarios such as Pressurized Thermal Shock (PTS), boron dilution, hydrogen build-up in containments, thermal fatigue and thermal striping issues, etc. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. Therefore, a set of ROCOM CFD-grade test data were made available to set up an IAEA benchmark, relating to Pressurized Thermal Shock (PTS) scenarios. The benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification. Data obtained from the PTS experiment were compared with predictions obtained from the CFD software ANSYS CFX.

The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: at higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this propagation. The ECC water falls in an almost vertical path and reaches the lower down-comer sen¬sor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. CFD was able to predict well the observed flow patterns and mixing phenomena.
Keywords: ROCOM, CFD, PTS, RPV, CFX, ECC, PWR
  • Lecture (Conference)
    Fourth Research Coordination Meeting on the Application of Computational Fluid Dynamics Codes for Nuclear Power Plant Design, 08.11.2017, Wien, Österreich

Publ.-Id: 26114 - Permalink


Ex-situ doping and Ohmic contact formation with low contact resistance on MBE grown GeSn on Si
Prucnal, S.; Augel, L.; Schulze, J.; Fischer, I. A.; Berencén, Y.; Hübner, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Wang, M.; Voelskow, M.; Helm, M.; Zhou, S.;
GeSn with quasi-direct band gap is one of the most promising semiconductor materials for light emitters integrated with CMOS technology. The equilibrium solid solubility limit (SSL) of Sn in Ge is in the range of 0.5 % and the predicted theoretical Sn concentration needed for the direct band gap formation is above 5 %. This means that GeSn with direct band gap is metastable and any related material process cannot be thermal equilibrium. Here we propose to utilize strongly non-equilibrium processing i.e. ion implantation followed by millisecond range flash lamp annealing (FLA), for doping and the formation of Ohmic contacts with low contact resistance on Ge0.95Sn0.05. The effective carrier concentration in P+ implanted Ge0.95Sn0.05 layer followed by FLA for 3 ms is above 5×10^19cm-3 with a specific contact resistance rc=4×10^-6Ωcm2. NiGe for Ohmic contact is made by Ni diffusion into GeSn during a single 3 ms long flash pulse. TEM images reveal that NiGe is polycrystalline but with an atomically sharp interface between the metal contact and GeSn. The influence of non-equilibrium processing (ion implantation and FLA) on the optical, electrical and microstructural properties of the GeSn layer grown by MBE on Si will be discussed in details.
Keywords: GeSn, MBE, doping, flash lamp annealing
  • Poster
    EMRS Fall Meeting 2017, 18.-21.09.2017, Warsaw, Poland

Publ.-Id: 26113 - Permalink


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